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Old 10-19-2018, 08:15 AM
aceplace57 aceplace57 is offline
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A math riddle for you. Feel free to submit your own.

I'll start with a classic math riddle. Please Submit your own favorites.

If your friend's son is four years old and his little brother is half his age (two years old), how old will the younger brother be if the older brother is 100?'


SPOILER:
98. The "half his age" is a red herring and useless information. Many people will insist the younger brother is 50.

Last edited by aceplace57; 10-19-2018 at 08:19 AM.
  #2  
Old 10-19-2018, 08:19 AM
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Originally Posted by aceplace57 View Post
I'll start with a classic math riddle. Please Submit your own favorites.

If your friend's son is four years old and his little brother is half his age (two years old), how old will the younger brother be if the older brother is 100?'


SPOILER:
98. The "half his age" is a red herring and useless information.
What is 2+2? Is it 5?

SPOILER:
No, it's 4. Mention of 5 was a red herring

Last edited by Mr Shine; 10-19-2018 at 08:20 AM.
  #3  
Old 10-19-2018, 08:23 AM
aceplace57 aceplace57 is offline
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You'd be surprised at how many people are fooled by the first riddle. I've used it as an ice breaker at conferences for years.
  #4  
Old 10-19-2018, 09:06 AM
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Divide 30 by a half and add 10

too many people don't think it through

(Not Dopers of course

SPOILER:
{70 not 25}

Last edited by spanna; 10-19-2018 at 09:07 AM.
  #5  
Old 10-19-2018, 09:10 AM
aceplace57 aceplace57 is offline
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I can easily see that riddle working.

People engaged in idle conversation often say the first and most obvious answer.
  #6  
Old 10-19-2018, 09:17 AM
Living Well Is Best Revenge Living Well Is Best Revenge is offline
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You'd be surprised at how many people are fooled by the first riddle. I've used it as an ice breaker at conferences for years.
What is it a conference for people with severe learning disabilities?
  #7  
Old 10-19-2018, 09:38 AM
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What is it a conference for people with severe learning disabilities?
That's not a math riddle!
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Old 10-19-2018, 10:29 AM
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There are people who could envision two young siblings growing up, and one ending up 50 years older than the other? My mind boggles.

A better riddle of this type, of which there are countless examples, is:

John is 3 times as old as Billy. In 6 years, John will be twice as old as Billy. How old are they now?

This is simple enough for most people to figure out (although probably not the ones who answered the OP's question incorrectly).
  #9  
Old 10-19-2018, 10:48 AM
pulykamell pulykamell is offline
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Originally Posted by Mr Shine View Post
What is 2+2? Is it 5?

SPOILER:
No, it's 4. Mention of 5 was a red herring
Pretty much my reaction. I thought, is there some word trickery I'm missing here? I hesitated for a minute, went with my answer, expected to have an "oh, shit! how did I miss that?" moment, but then, no, it was exactly the answer I'd expect anyone would get. I mean, hopefully the OP at least leaves off the parenthetical "two years old" part. Then I could see at least some people getting tricked.

Last edited by pulykamell; 10-19-2018 at 10:48 AM.
  #10  
Old 10-19-2018, 10:48 AM
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There are people who could envision two young siblings growing up, and one ending up 50 years older than the other? My mind boggles
Not really. That's what makes riddles such as that one fun for some people. They quickly figure (especially if asked orally) they just cut the age in half. After they're told the answer, they slap their forehead because they fell for it. Here's a non-math riddle told orally following that premise that is told by kids:

Spell so (kid spells so)
Spell foe (kid spells foe)
Spell no (kid spells no)

What do you do at a red light?

Of course kids know that you stop. But if they fall for it...
  #11  
Old 10-19-2018, 10:53 AM
pulykamell pulykamell is offline
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As a kid, one of my favorite misdirection groaner versions of this type of puzzle started with "Ok, you're [or I'm] driving a bus. At the first stop X amount of people get on. At the next stop, half the people get off, and 3 people get on." And then you just spin in with some types of seemingly complicated, but doable math for a couple rounds. At the end, the question is "what is the name of the bus driver?"

Well, it's there in the first sentence.

My father drove me nuts, because I've heard my father tell that riddle, and completely forget the first sentence as, you know, kinda being the key to it all, so it just ended up completely non-sensical in the end. Or maybe he was trying to some abstract Kaufmann shit, I don't know.

Last edited by pulykamell; 10-19-2018 at 10:56 AM.
  #12  
Old 10-19-2018, 10:57 AM
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Originally Posted by aceplace57 View Post
You'd be surprised at how many people are fooled by the first riddle. I've used it as an ice breaker at conferences for years.
It would probably have worked better if you left out the parenthetical "(two years old)."
  #13  
Old 10-19-2018, 11:01 AM
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  1. Three horses are running at 30 miles per hour. What is the speed of one horse?
  2. A bucket of 90 degree water is added to a bucket of 90 degree water. How hot is the resulting water?
  3. You have a dozen cookies. You eat all but three of them. How many cookies do you have left?
  #14  
Old 10-19-2018, 11:14 AM
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A man offers you a car if you can choose which one of three doors it's behind. Behind the other 2 are goats. After you choose, he opens one of the other doors and reveals a goat. He then offers you the chance to switch doors. Should you, or does it not matter?

SPOILER:
You should definitely not switch. The only reason someone would add this option in after the fact is if you chose the car straight away.
  #15  
Old 10-19-2018, 11:15 AM
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Some of my favorites:

Joey has two pencils. One is an expensive pencil, and one is a cheap one. The expensive pencil costs $1.00 more than the cheap one. He spent $1.10 total. How much was the cheap pencil?

The others I'll post links to:

https://boards.straightdope.com/sdmb...d.php?t=136384

https://en.wikipedia.org/wiki/Hat_pu...nd_hats_puzzle
  #16  
Old 10-19-2018, 11:26 AM
aceplace57 aceplace57 is offline
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Originally Posted by Thudlow Boink View Post
It would probably have worked better if you left out the parenthetical "(two years old)."
I do leave it out when speaking the riddle. I'm not sure why I added it in written form.
  #17  
Old 10-19-2018, 11:33 AM
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A man drives to visit a friend. He averages 20 miles per hour for the trip. How fast does he have to drive on the trip back home to average 40 mph for the whole round trip?

SPOILER:

No, it's not 80, or whatever number you were thinking of. It's impossible. He'd have to make the return trip in zero time to average 40 mph for the round trip.
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Old 10-19-2018, 11:35 AM
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nm

Last edited by markn+; 10-19-2018 at 11:39 AM.
  #19  
Old 10-19-2018, 11:43 AM
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Originally Posted by markn+ View Post
A man drives to visit a friend. He averages 20 miles per hour for the trip. How fast does he have to drive on the trip back home to average 40 mph for the whole round trip?

SPOILER:

No, it's not 80, or whatever number you were thinking of. It's impossible. He'd have to make the return trip in zero time to average 40 mph for the round trip.
I was lazy and linked to the same riddle instead of writing it out. Definitely a good one as it's not too easy or too hard.
  #20  
Old 10-19-2018, 11:52 AM
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Originally Posted by pulykamell View Post
As a kid, one of my favorite misdirection groaner versions of this type of puzzle started with "Ok, you're [or I'm] driving a bus. At the first stop X amount of people get on. At the next stop, half the people get off, and 3 people get on." And then you just spin in with some types of seemingly complicated, but doable math for a couple rounds. At the end, the question is "what is the name of the bus driver?"
The way I've always heard this one is the final question is "how many stops did the bus make"? I think this is better because the answer similarly turns out to be much simpler than expected, but in this case the questionee won't be able to give the right answer (assuming he was keeping track of the passengers rather than the stops).
  #21  
Old 10-19-2018, 12:01 PM
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Related to the riddle in the OP

A man asks his son: Right now I'm three times as old as you. in 10 years I will be only twice as old as you. How long before we're the same age?

Last edited by Buck Godot; 10-19-2018 at 12:01 PM.
  #22  
Old 10-19-2018, 12:58 PM
pulykamell pulykamell is offline
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The way I've always heard this one is the final question is "how many stops did the bus make"? I think this is better because the answer similarly turns out to be much simpler than expected, but in this case the questionee won't be able to give the right answer (assuming he was keeping track of the passengers rather than the stops).
Ah, yes! That's another variation I've heard. Forgot about that one.
  #23  
Old 10-19-2018, 01:19 PM
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A man offers you a car if you can choose which one of three doors it's behind. Behind the other 2 are goats. After you choose, he opens one of the other doors and reveals a goat. He then offers you the chance to switch doors. Should you, or does it not matter?

SPOILER:
You should definitely not switch. The only reason someone would add this option in after the fact is if you chose the car straight away.
There are lies, there are damned lies, and there are statistics.
Nonetheless, choosing between three doors yields a 33% success rate. Choosing between two doors gives a 50% success rate.
  #24  
Old 10-19-2018, 01:30 PM
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There are lies, there are damned lies, and there are statistics.
Nonetheless, choosing between three doors yields a 33% success rate. Choosing between two doors gives a 50% success rate.
Only if the two doors have an equal probability of having the car behind it. Which is not the case in the classic example (The Monty Hall Problem) Mr Shine riffed off of.
  #25  
Old 10-19-2018, 02:10 PM
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Quote:
Originally Posted by Mr Shine View Post
A man offers you a car if you can choose which one of three doors it's behind. Behind the other 2 are goats. After you choose, he opens one of the other doors and reveals a goat. He then offers you the chance to switch doors. Should you, or does it not matter?

SPOILER:
You should definitely not switch. The only reason someone would add this option in after the fact is if you chose the car straight away.
This is the infamous "Monty Hall Problem" named after the original Let's Make A Deal and it's host. There is an existing thread that went on for a thousand pages.

"The only reason someone would add this option in after the fact is if you chose the car straight away" is not part of the Monty Hall Problem - in it he always offers you a switch after showing one of the doors (and he knows what's behind the doors and will never show you the good prize).

And it's actually quite simple: switching will improve your odds to 2/3 - your original pick is wrong 2 times out of three, in those cases switching will make you a winner. In other words, switching is only wrong if you originally had the correct door.
  #26  
Old 10-19-2018, 02:17 PM
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A stupid dad joke my dad used to tell me:

A forest covers 500 acres, how far can a tiger walk into the forest?

SPOILER:
half way, after that the tiger is walking OUT of the forest
  #27  
Old 10-19-2018, 02:22 PM
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"The only reason someone would add this option in after the fact is if you chose the car straight away" is not part of the Monty Hall Problem
Right, which is why his answer differs from the original. I think Mr Shine is aware of how it usually goes.
  #28  
Old 10-19-2018, 02:36 PM
iamthewalrus(:3= iamthewalrus(:3= is offline
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There's at least a little bit of ambiguity in the phrasing of the question in the OP that might lead people to misunderstand.

"how old will the younger brother be if the older brother is 100?"

Could be interpreted as "Ok, now here's another scenario where an older brother is 100 and a younger brother is half his age".

I'm not saying that's the best interpretation, but it's at least a conceivably rational one. People are used to getting multiple "math questions" where part of the premise of the question stays the same (half his age) and another part varies (the age that is to be halved). It's not 100% clear that the second question means "this same pair of brothers 96 years later".
  #29  
Old 10-19-2018, 02:56 PM
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Here is one from Car Talk, abridged:

RAY: Potatoes are 99 percent water. So say you take 100 pounds of potatoes and you set them out on your back porch to dry out. After a while, enough water has evaporated so that they are now 98 percent water. If you were to weigh those potatoes at that moment...

TOM: 99 pounds.

RAY: You are wrong.

SPOILER:

RAY: Now, unencumbered by the thought process as usual, my brother guessed 99 pounds.

TOM: Yeah.

RAY: Now, when I guessed, off the top of my head, I guessed about 90 pounds.

TOM: 'Cause it just feels right.

RAY: But if you do the math, 1 percent of 100 --which is what the potato is-- is one pound. As we told you, that's 1 percent. So 2 percent, when it’s 98 percent water, two percent of the new weight of the mass is still going to be equal to that one pound, and 2 percent of 50 pounds is a pound. So the potato weight is now 50 pounds, not 100.
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  #30  
Old 10-19-2018, 03:06 PM
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There's at least a little bit of ambiguity in the phrasing of the question in the OP that might lead people to misunderstand.

"how old will the younger brother be if the older brother is 100?"

Could be interpreted as "Ok, now here's another scenario where an older brother is 100 and a younger brother is half his age".

I'm not saying that's the best interpretation, but it's at least a conceivably rational one. People are used to getting multiple "math questions" where part of the premise of the question stays the same (half his age) and another part varies (the age that is to be halved). It's not 100% clear that the second question means "this same pair of brothers 96 years later".
I agree. It can be read to be saying "One brother is twice as old as the other. If the older brother is four, then the younger brother is two. If the older brother is one hundred, then the younger brother is fifty."

I think the second part of the question should be "how old will the younger brother be when the older brother is 100?" to eliminate that ambiguity.
  #31  
Old 10-19-2018, 03:14 PM
F. U. Shakespeare F. U. Shakespeare is offline
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A variation of a joke from "Hee Haw":

At the age of 30, a woman gives birth to a daughter.

Ten years later, the daughter is 10, and the mother is 40, or four times as old.

Five more years later, the daughter is fifteen, and the mother is 45, or only three times as old.

Fifteen more years later, the daughter is thirty, and the mother is 60, or only twice as old.

Question: how long until they're both the same age?

Last edited by F. U. Shakespeare; 10-19-2018 at 03:15 PM.
  #32  
Old 10-19-2018, 03:15 PM
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Quote:
Originally Posted by aceplace57 View Post
I'll start with a classic math riddle. Please Submit your own favorites.

If your friend's son is four years old and his little brother is half his age (two years old), how old will the younger brother be if the older brother is 100?'


SPOILER:
98. The "half his age" is a red herring and useless information. Many people will insist the younger brother is 50.
ISTM that you'd be on solid ground if the sentence read "when the older brother is 100."

But "if the older brother is 100" - OK, we're tossing out the notion that he's 4 now, and replacing that by his being 100 now, not 96 years from now, but keeping everything else the same. In that case, we've got to choose between little brother being half his age (in the sentence proper) or two years old (in the parenthetical). So either 50 or 2. I'd insist on 50 as well.
  #33  
Old 10-19-2018, 03:31 PM
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Here's one that I came up with myself (well, took an extremely simple puzzle and complicated it):

My first job was for a bottled tea company. We sold tea in cases of 100, and we sold three kinds of cases: sweet tea, unsweet tea, and assorted (50 each sweet and unsweet). The tea looked the same, only the labels were different.

I was the delivery driver, and my first day, I had a case of each to deliver. Just as I was getting ready to leave, my boss got a call from the bottling factory. "We got a problem," the bottle-labeler said. "I noticed that the labeling machine was broken, so none of the bottles got labels."

"Crap," my boss said. "Okay, we'll send them back. Put sweet labels on the ones in the sweet case, put unsweet labels on the one in the unsweet case, and I dunno, throw away the ones in the assorted case, no fixing that one."

"Uh, there's another problem. I noticed that the case labeler mixed up the labels. There is definitely one case of each, but it put the wrong label on each case."

"Dammit. Which label went on which case?"

"Uh, I forget?"

My boss hung up. "Okay, first thing we do, we fire that guy, that guy is terrible. But now we're gonna have to start tasting bottles of tea until we figure out which case has both sweet tea and unsweet tea in it, and then we'll be able to figure things out, but who knows how many bottles we'll have to go through and waste? This is a disaster!"

"Actually," I said, "I can fix it by tasting a single bottle: one sip, and I'll tell you which label to put on which case. As a bonus, I can tell you how to salvage the case of assorted tea."

How did I do it?

Last edited by Left Hand of Dorkness; 10-19-2018 at 03:32 PM.
  #34  
Old 10-19-2018, 03:35 PM
Hari Seldon Hari Seldon is offline
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Here is one that's a bit harder. You core an apple and the cored apple that remains is 4 inches high. What is its volume (the cored apple). Assume the apple started out as a perfect sphere.

SPOILER:
You could do this using calculus (I have checked the answer that way), but if you simply assume that there is an answer independent of the original size of the apple, you conclude that it must be the same if the core is 0 and the apple was originally 4" high. In that case its radius is 2" and its volume is 4*pi*r^3/3 = 32*pi/3
  #35  
Old 10-19-2018, 04:53 PM
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Quote:
Originally Posted by Left Hand of Dorkness View Post
Here's one that I came up with myself (well, took an extremely simple puzzle and complicated it):

My first job was for a bottled tea company. We sold tea in cases of 100, and we sold three kinds of cases: sweet tea, unsweet tea, and assorted (50 each sweet and unsweet). The tea looked the same, only the labels were different.

I was the delivery driver, and my first day, I had a case of each to deliver. Just as I was getting ready to leave, my boss got a call from the bottling factory. "We got a problem," the bottle-labeler said. "I noticed that the labeling machine was broken, so none of the bottles got labels."

"Crap," my boss said. "Okay, we'll send them back. Put sweet labels on the ones in the sweet case, put unsweet labels on the one in the unsweet case, and I dunno, throw away the ones in the assorted case, no fixing that one."

"Uh, there's another problem. I noticed that the case labeler mixed up the labels. There is definitely one case of each, but it put the wrong label on each case."

"Dammit. Which label went on which case?"

"Uh, I forget?"

My boss hung up. "Okay, first thing we do, we fire that guy, that guy is terrible. But now we're gonna have to start tasting bottles of tea until we figure out which case has both sweet tea and unsweet tea in it, and then we'll be able to figure things out, but who knows how many bottles we'll have to go through and waste? This is a disaster!"

"Actually," I said, "I can fix it by tasting a single bottle: one sip, and I'll tell you which label to put on which case. As a bonus, I can tell you how to salvage the case of assorted tea."

How did I do it?
The first part is a classic problem I'll just leave alone. For the second,

SPOILER:
Mix them all together and market the bottles as a special "Sweet tea lite"?

Edit: No, just got it, mix them all together and then add the right amount of sugar to bring it up to sweetened

Last edited by Mr Shine; 10-19-2018 at 04:55 PM.
  #36  
Old 10-19-2018, 05:41 PM
iamthewalrus(:3= iamthewalrus(:3= is offline
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Originally Posted by Left Hand of Dorkness View Post
"Uh, there's another problem. I noticed that the case labeler mixed up the labels. There is definitely one case of each, but it put the wrong label on each case."
<snip>
"Actually," I said, "I can fix it by tasting a single bottle: one sip, and I'll tell you which label to put on which case. As a bonus, I can tell you how to salvage the case of assorted tea."

How did I do it?
Do we read the "wrong label on each case" explicitly. Not, like, the labels were put on in an unknown manner, but for sure, each case is something other than it's labeled?

If so,
SPOILER:
taste a bottle from the case labeled "assorted". If it's sweet, that's the sweet case. If it's not, that's the unsweet case. Put the correct label on it, put the assorted label on the other labeled box, put the other label on the box you took a label off to put on the box you tasted from.


One of my favorite math puzzlers is with a standard 5-card hand from a standard 52-card deck.

One player looks at the 5 cards, removes one card face down. Passes a pile of the other 4 cards to the second player. The second player looks at the 4 cards and names the face-down card he hasn't seen. The two players are allowed to come up with a strategy before playing, but they don't know which 5 cards are in the hand.

How do you do it?
  #37  
Old 10-19-2018, 06:01 PM
Little Nemo Little Nemo is offline
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Originally Posted by Mr Shine View Post
For the second,

SPOILER:
Mix them all together and market the bottles as a special "Sweet tea lite"?

Edit: No, just got it, mix them all together and then add the right amount of sugar to bring it up to sweetened
I came up with a different solution.

SPOILER:
Label the assorted case as mystery tea and sell it as is.
  #38  
Old 10-19-2018, 06:41 PM
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Originally Posted by iamthewalrus(:3= View Post
One of my favorite math puzzlers is with a standard 5-card hand from a standard 52-card deck.

One player looks at the 5 cards, removes one card face down. Passes a pile of the other 4 cards to the second player. The second player looks at the 4 cards and names the face-down card he hasn't seen. The two players are allowed to come up with a strategy before playing, but they don't know which 5 cards are in the hand.

How do you do it?
SPOILER:
"When you hand me the four cards, say the name of the card you kept out loud."
"Okay!"
  #39  
Old 10-19-2018, 06:59 PM
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Decide on an order of the deck (eg. A-K of hearts, then A-K of diamonds, then clubs, then spades). Thus each card has an index number (1 = ace of hearts, 2 = deuce of hearts, etc.) When the first player gets the 5 cards, he removes a card which has index number N, waits N seconds, then pass the four cards to the other player.
  #40  
Old 10-19-2018, 07:37 PM
begbert2 begbert2 is offline
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Quote:
Originally Posted by markn+ View Post
Decide on an order of the deck (eg. A-K of hearts, then A-K of diamonds, then clubs, then spades). Thus each card has an index number (1 = ace of hearts, 2 = deuce of hearts, etc.) When the first player gets the 5 cards, he removes a card which has index number N, waits N seconds, then pass the four cards to the other player.
Well, if you're going to go to the trouble of numbering all the cards in the deck, you can
SPOILER:
Have the first player carefully reorder and position the cards - there are 24 different ways to order four cards with different values, and 16 different ways to position four cards where either can be upright or sideways. That means there's 384 different ways you can pile up four arbitrary cards, so with some hardcore preplanning and memorization the identity of the removed card can be encoded by the first player and interpreted by the second.
  #41  
Old 10-19-2018, 10:01 PM
aceplace57 aceplace57 is offline
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I'll take my time going through the riddles/puzzles posted.

I like to work it out for myself before reading the solution.

I used to buy the math puzzle books. That was decades ago. I've slowed down since then.

Many of the adult books require statistics and I never took that in college. I got a taste of it in Algebra II and knew statistics wasn't where my talents lay. I'm better at working equations in Physics and electronics.

Last edited by aceplace57; 10-19-2018 at 10:06 PM.
  #42  
Old 10-20-2018, 12:23 AM
Doug K. Doug K. is offline
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What's the relationship between Salagadoola and Mechika Boola?

SPOILER:

Salagadoola + Mechika Boola + Bibbidi-bobbidi-boo = Bibbidi-bobbidi-boo.
Subtract Bibbidi-bobbidi-boo from both sides:
Salagadoola + Mechika Boola = 0

Subtract Mechika Boola from both sides:
Salagadoola = -Mechika Boola
  #43  
Old 10-20-2018, 01:33 AM
UltraVires UltraVires is offline
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Quote:
Originally Posted by Left Hand of Dorkness View Post
Here's one that I came up with myself (well, took an extremely simple puzzle and complicated it):

My first job was for a bottled tea company. We sold tea in cases of 100, and we sold three kinds of cases: sweet tea, unsweet tea, and assorted (50 each sweet and unsweet). The tea looked the same, only the labels were different.

I was the delivery driver, and my first day, I had a case of each to deliver. Just as I was getting ready to leave, my boss got a call from the bottling factory. "We got a problem," the bottle-labeler said. "I noticed that the labeling machine was broken, so none of the bottles got labels."

"Crap," my boss said. "Okay, we'll send them back. Put sweet labels on the ones in the sweet case, put unsweet labels on the one in the unsweet case, and I dunno, throw away the ones in the assorted case, no fixing that one."

"Uh, there's another problem. I noticed that the case labeler mixed up the labels. There is definitely one case of each, but it put the wrong label on each case."

"Dammit. Which label went on which case?"

"Uh, I forget?"

My boss hung up. "Okay, first thing we do, we fire that guy, that guy is terrible. But now we're gonna have to start tasting bottles of tea until we figure out which case has both sweet tea and unsweet tea in it, and then we'll be able to figure things out, but who knows how many bottles we'll have to go through and waste? This is a disaster!"

"Actually," I said, "I can fix it by tasting a single bottle: one sip, and I'll tell you which label to put on which case. As a bonus, I can tell you how to salvage the case of assorted tea."

How did I do it?
Point of clarification. Do we know absolutely that the case labels are wrong, or were they just randomly assigned such that the labels (one or more) may be accidentally correct?
  #44  
Old 10-20-2018, 03:01 AM
Little Nemo Little Nemo is offline
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Quote:
Originally Posted by Doug K. View Post
What's the relationship between Salagadoola and Mechika Boola?

SPOILER:

Salagadoola + Mechika Boola + Bibbidi-bobbidi-boo = Bibbidi-bobbidi-boo.
Subtract Bibbidi-bobbidi-boo from both sides:
Salagadoola + Mechika Boola = 0

Subtract Mechika Boola from both sides:
Salagadoola = -Mechika Boola
Incorrect.

SPOILER:
You forgot that Salagadoola means Mechicka Boola.

Therefore in addition to:
Salagadoola + Mechika Boola + Bibbidi-bobbidi-boo = Bibbidi-bobbidi-boo

You also know:
Salagadoola = Mechika Boola

Salagadoola and Mechicka Boola must both equal zero to make both equations correct.

Last edited by Little Nemo; 10-20-2018 at 03:02 AM.
  #45  
Old 10-20-2018, 03:13 PM
vperry1 vperry1 is offline
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Not a math puzzle, but mathematically comical and true.

My brother walked in to a pizza joint and ordered a pizza. The pizza cook took the pie from the oven and asked:

Pizza cook: "Are you on a diet?"

Brother: (slightly offended) "No. Why?"

Pizza cook: "Well, if you were, I'd cut this into 6 slices instead of 8."
__________________
Hypocrisy is the main contributor to imperfection.
  #46  
Old 10-20-2018, 08:26 PM
Malleus, Incus, Stapes! Malleus, Incus, Stapes! is offline
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Quote:
Originally Posted by markn+ View Post
The way I've always heard this one is the final question is "how many stops did the bus make"?
I've heard it as "What color is the bus driver's eyes?"

Quote:
I think this is better because the answer similarly turns out to be much simpler than expected, but in this case the questionee won't be able to give the right answer (assuming he was keeping track of the passengers rather than the stops).

What you said is logical, but by the time the teller gets to the end of the riddle, I think most people have forgotten the wording at the beginning. (There's a riddle that goes something like "Karen's mother has four children: Penny, Nicholas, and Dime. What is the fourth child's name?" Shorter than the bus one, but many people have already edited the "extraneous" opening details out of their minds by the time you're done).

(On that note, I think you guys should really lay off of Acey. People will very often say a stupid "obvious" answer because the way the question was asked short-circuits their brains).

Last edited by Malleus, Incus, Stapes!; 10-20-2018 at 08:30 PM.
  #47  
Old 10-21-2018, 10:41 AM
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Biotop Biotop is offline
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Before each game of the upcoming World Series, the Dodgers and Red Sox will engage in competitive coin flipping. Each team will gather and at a signal each manager will flip a quarter and record the results. They will then again flip their quarters and record the results. Each team's manager will continue simultaneously to flip their coins until one team wins the day's competition.

The Dodgers will win if at some point they flip a head and next a tail. The Red Sox will win if they at some point flip a head and then next a head. If the two teams win at the same time the result is a tie. If there is a tie results are scrapped and the day's flipping competition must start over.

Each day you have the opportunity to bet on either the Dodgers or Red Sox to win the coin flip competition. Which team do you choose?
  #48  
Old 10-21-2018, 11:38 AM
Lucas Jackson Lucas Jackson is offline
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Quote:
Originally Posted by Hari Seldon View Post
Here is one that's a bit harder. You core an apple and the cored apple that remains is 4 inches high. What is its volume (the cored apple). Assume the apple started out as a perfect sphere.

SPOILER:
You could do this using calculus (I have checked the answer that way), but if you simply assume that there is an answer independent of the original size of the apple, you conclude that it must be the same if the core is 0 and the apple was originally 4" high. In that case its radius is 2" and its volume is 4*pi*r^3/3 = 32*pi/3
Some of these arent riddles in the sense of the OP, they are just math problems.
  #49  
Old 10-21-2018, 11:52 AM
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Quote:
Originally Posted by Lucas Jackson View Post
Some of these arent riddles in the sense of the OP, they are just math problems.
True, but a good math puzzle riddle (i.e. Monty Hall) will often have an "easy" answer that turns out to be wrong because of... math. Other riddles the math is straightforward, but the wording of the riddle is the trick. Both qualify as math riddles to me.
  #50  
Old 10-21-2018, 12:04 PM
Dickerman Dickerman is offline
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For the OP, the correct answer is the younger brother is almost certainly dead.
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