Like gigi, but I break it up according to each place and then add the totals together.
300+300 (or 300x2, depending on my mood) = 600
60+60 = 120
5+5 = 10
730
Similar structure for multiplication and adding large numbers. My mom tried to teach me this back in 4th grade or so, but it just didn’t stick. I realized long about 11th grade what she was talking about and went to her excitedly, saying, “Hey, I understand it now!” “What?” she asked. “Addng in my head!” I say. “Well, it took you long enough.” Oh mom, where would I be without your encouragement?
(disclaimer: She actually was quite encouraging. She’s just also kinda mean in a lovable mom sort of way.)
That’s what I do but in my head it looks something like a slot machine, or maybe Connect Four but with numbers instead of little red disks.
It didn’t take a terribly long time. Does that make sense?
And that’s the only hard term in the original question.
Now I returned to the original terms which are “simpler” and kept a running total: 300300 = 90,000
230065 = 300130 = 39,000 (total 129,000)
Finally add in the funny number (that’s how I think of it), 4225 and you get 133,225.
Got it right the first time, took a minute or three in my head. I’m pretty good with multiplying two digit numbers mentally. I generally find it easier to express them as (a+b) rather than (a-b) because in the former case, all of your operations are addition whereas in the latter you have some addition and some subtraction, I find that I start making mistakes adding when I should have been subtracting, or vice versa.
Whaat? Do you think most people can multiply 3-didjit numbers in their heads? Are folks in general *expected *to be able to do that kind of multiplication in their heads?
Because there is just no fucking way I can do that, not to save my ass from a firing squad or to win a zillion dollars tax-free. It wouldn’t be a matter of just getting the answer wrong, either; manipulating that many numbers mentally without dicking it out in pencil is flat out impossible for me. I thought it was only real math whizzes who could do shit like that.
“Easy enough”, s/he says. “8 seconds.”
I knew I was just a half-step up from a practical innumerate already (hell, I can’t count past ten if I’ve got shoes on ) but the inference that intelligent people do sums like that in their heads every day as a matter of course, tells me maybe I oughtta just put on this nice pointy paper hat…and climb up on this five-foot stool back here in the corner…and whimper to myself, very quietly, for the rest of the day .
Now that just literally makes my head hurt trying to follow it.
The only way I know to find 365 times 365 is with a pencil on scrap paper, and I’d probably need the better part of a minute to dope it out.
I’m not trying to mess with you, OP, it just slays me that you, and the folks you aimed your query to, can figure that out in your mind in just seconds, like it was nothing, while I would have to sweat it out like a dog shitting peach pits.
good grief, it gives me a headache just thinking about it. i can not juggle that many numbers in my head and have them land properly.
were i to attempt such a thing without a calculator i would…figure on it being about 2 years.
if that didn’t fly. it would be 5+5=0 carry a 1… 6+6=12+1=3 carry a 1… 3+3=6+1=7 so that will be seven three zero.
if i were multiplying them you may as well sit down for 2 years… here we go:
5 time 5 is 5 carry a 2. 5 times 6 is 0 +2=2 carry a 3, 5 times 3 is 15+3=18 so first line is 1835
onward to the second line… six times 5 is 0 carry a 3, six times six is 6 plus 3=9 carry a 3, six times 3 is 18 +3= 21 so second line is 2190
and still we juggle… 3 time 5 is 5 carry a 1, 3 times 6 is 8 +1=9 carry a one 3 time 3 is 9 plus one is 10 so third line is 1095
at this point my brain shuts down because i am now juggling 3 set of 4 numbers and have forgotten the first set completly and def. need paper or a calculator and start over.
i am in utter awe of people who can make numbers dance to their tune. complete and utter awe.
I use 90wt’s method, only I did the 300s first. plus the internal dialogue is like “Two three hundreds is six hundred plus two 65s, 130. Uhh what was the first number, oh yeah 600 plus those two 65s again, 130…730. OK, yeah…”
I use ‘round up and subtract the difference’ When the number is close to an ordinal. (That the right term?)
That’s what people say when I explain how I do averages in my head.
Say you want to average 65, 72, and 85:
first, subtract 65 from the higher numbers (so all the numbers are the same, you see) = 7, 20
then add those numbers together = 27
now divide by three (since you now have 3 65s off over there)= 9
last add that 9 to 65 = 74 so that’s the average. 74.
This works for me with up to 5 or 6 numbers before I get confused by what I’m keeping track of in the second step.
Well, first I convert to binary: 101101101 + 101101101. Then, I load the rightmost digit into my A register … Well, the rest should be pretty obvious, right?
As a former roulette dealer, I’ve learned/was taught to add the 100’s first, then 10’s, then 1’s. It is something that you REALLY need to do in order not to lose things in the muck that is your thoughts. And now, I just apply that to everything, which is awesome, because my Arts degree brain is a zillion times faster at basic math than my Science PhD boyfriend’s.
However, you stick some X’s, Y’s, Z’s… or any other symbol, and he wins, hands down!
) but the inference that intelligent people do sums like that in their heads every day as a matter of course, tells me maybe I oughtta just put on this nice pointy paper hat…and climb up on this five-foot stool back here in the corner…and whimper to myself, very quietly, for the rest of the day .
