# Math puzzle driving me crazy
**URL:** https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289
**Category:** Miscellaneous and Personal Stuff I Must Share
**Created:** [August 11, 2006, 3:46pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289 "2006-08-11T15:46:22Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@jjimm](https://boards.straightdope.com/u/jjimm)
#### Post date: [August 11, 2006, 3:46pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/1 "2006-08-11T15:46:22Z")
Received this at work - the sender says he knows the answer, and it’s completely possible using the rules set down:
You have the numbers 1, 7, 7, 7 and 7 (that’s four sevens and a one).
You may use any of the conventional mathematical operators (add,
subtract, multiply and divide) and you may use brackets. You do NOT need
to do anything tricky like ‘sticking’ numbers together (such as making
two 7s into 77). Your target is to make exactly 100. This is not a trick
question.
I’ve resigned myself to not solving it myself, so don’t feel that I’m cheating, and I will not pretend that the answer is my own. Any ideas? I’m going nuts over it.
---
### Author:  [@Pixisis](https://boards.straightdope.com/u/Pixisis)
#### Post date: [August 11, 2006, 3:50pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/2 "2006-08-11T15:50:00Z")
[spoiler]
1+ 7 x 7 + 7 x 7
or to be more clear 1 + (7 x 7) + (7 x 7) [/spoiler]
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### Author:  [@Pixisis](https://boards.straightdope.com/u/Pixisis)
#### Post date: [August 11, 2006, 3:51pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/3 "2006-08-11T15:51:02Z")
NO ! :smack: i’m idiot. ignore me.
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### Author:  [@twickster](https://boards.straightdope.com/u/twickster)
#### Post date: [August 11, 2006, 3:55pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/4 "2006-08-11T15:55:00Z")
> [@Pixisis](#):
>
> NO ! :smack: i’m idiot. ignore me.
yeah, I did the exact same thing.
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### Author:  [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)
#### Post date: [August 11, 2006, 3:57pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/5 "2006-08-11T15:57:57Z")
Here’s a trick answer that’s almost certainly cheating:
Turn two of the 7s upside down so that they look like Ls.
Then L + L + [(7/7) – 1] = 100.
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### Author:  [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)
#### Post date: [August 11, 2006, 4:00pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/6 "2006-08-11T16:00:16Z")
(7/7)+((7+7)\*7)+1
You have just witnessed an amazing feat ladies and gentleman, as I am president of the “Bad Math Club.” Just yesterday I had to ask someone how to do X = 2% \* Y for Y. I am amazed, myself.
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### Author:  [@Crotalus](https://boards.straightdope.com/u/Crotalus)
#### Post date: [August 11, 2006, 4:01pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/7 "2006-08-11T16:01:12Z")
> [@Thudlow Boink](#):
>
> Here’s a trick answer that’s almost certainly cheating:
>
> Turn two of the 7s upside down so that they look like Ls.
> Then L + L + [(7/7) – 1] = 100.
Cheating or not, I think that is brilliant, Thudlow.
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### Author:  [@twickster](https://boards.straightdope.com/u/twickster)
#### Post date: [August 11, 2006, 4:01pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/8 "2006-08-11T16:01:32Z")
> [@ZipperJJ](#):
>
> (7/7)+((7+7)\*7)+1
>
> .
But that’s 5 7’s, not 4.
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### Author:  [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)
#### Post date: [August 11, 2006, 4:01pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/9 "2006-08-11T16:01:51Z")
ROTFL that’s 5 sevens.
See, I knew it was too good to be true 🙂
I am no longer amazed and can now retreat back to the Land Without Math.
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### Author:  [@Crotalus](https://boards.straightdope.com/u/Crotalus)
#### Post date: [August 11, 2006, 4:02pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/10 "2006-08-11T16:02:14Z")
> [@ZipperJJ](#):
>
> (7/7)+((7+7)\*7)+1
>
> You have just witnessed an amazing feat ladies and gentleman, as I am president of the “Bad Math Club.” Just yesterday I had to ask someone how to do X = 2% \* Y for Y. I am amazed, myself.
Too many sevens, I think.
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### Author:  [@Baron\_Greenback](https://boards.straightdope.com/u/Baron_Greenback)
#### Post date: [August 11, 2006, 4:02pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/11 "2006-08-11T16:02:30Z")
**ZipperJJ** your solution has one 7 too many…
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### Author:  [@JustAnotherGeek](https://boards.straightdope.com/u/JustAnotherGeek)
#### Post date: [August 11, 2006, 4:04pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/12 "2006-08-11T16:04:58Z")
I could do it with _five_ sevens.
1+(7_7)_((7+7)/7)
Still working on the four seven version.
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### Author:  [@JustAnotherGeek](https://boards.straightdope.com/u/JustAnotherGeek)
#### Post date: [August 11, 2006, 4:06pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/13 "2006-08-11T16:06:31Z")
I swear **ZipperJJ** ’s post wasn’t there!
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### Author:  [@Baron\_Greenback](https://boards.straightdope.com/u/Baron_Greenback)
#### Post date: [August 11, 2006, 4:09pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/14 "2006-08-11T16:09:29Z")
(7+7) \* (7+(1/7))
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### Author:  [@jjimm](https://boards.straightdope.com/u/jjimm)
#### Post date: [August 11, 2006, 4:11pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/15 "2006-08-11T16:11:11Z")
Yay **Struan**!!!
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### Author:  [@mittu](https://boards.straightdope.com/u/mittu)
#### Post date: [August 11, 2006, 4:13pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/16 "2006-08-11T16:13:01Z")
/applause **Struan**
That was driving me mad, thanks for putting me out of my misery.
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### Author:  [@Mindfield](https://boards.straightdope.com/u/Mindfield)
#### Post date: [August 11, 2006, 4:16pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/17 "2006-08-11T16:16:07Z")
> [@Struan](#):
>
> (7+7) \* (7+(1/7))
I think he’s got it.
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### Author:  [@twickster](https://boards.straightdope.com/u/twickster)
#### Post date: [August 11, 2006, 4:19pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/18 "2006-08-11T16:19:10Z")
So is someone going to cough up the $7 + $7 +$1 for **Struan** ’s membership?
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### Author:  [@Pixisis](https://boards.straightdope.com/u/Pixisis)
#### Post date: [August 11, 2006, 4:23pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/19 "2006-08-11T16:23:04Z")
my hat’s off to you, **Straun**!
now i can move on to other ways to embarrass myself …
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### Author:  [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)
#### Post date: [August 11, 2006, 4:41pm UTC](https://boards.straightdope.com/t/math-puzzle-driving-me-crazy/368289/20 "2006-08-11T16:41:48Z")
You guys need to be more _rational_:
(7 + 7)(7 + 1/7) = 100
Stranger
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