Mental Math

[Anonymous No.7042439]

How many of you would consider yourselves good at doing mental math?

I'm talking things like being able to solve problems such as 24 * 36 or 19894 + 741 under 2 and a half minutes. If so, how did you train yourselves to be able to do it?

[Anonymous No.7042459]

take alot of algebra and see those simply as variables, then simplify

[Anonymous No.7042467]

>>7042439
with enough practice you can see things

like 24 is 2/3 of 36
so 36 squared by 2/3 is 864

19894 is 200 and 6 from 2,000 which is about 1%

741*20,000= 14,820,000 + 1482*3 is roughly 4500
=14824500

minus 1% is 14,68x,xxx

when I punch the calculator, it shows me how wrong I am
usually within the bounds of 3% is fine with me, a statistical substance is good enough for resolving any math problem that doesn't need to be calculated to an exact degree, and we don't rely on humans to calculate exact degrees so we have calculators.

I just realized you used a plus sign.

fuck

[Anonymous No.7042478]

Or you could just... chunk them. I don't know what the proper term is, but it's that thing you do when you have to deal with large numbers in a hurry. Take out the factors that make them big and put them back in once you solved the inner part of the expression. Or take out one set of factors in one multiplicand and put them in the other until it's easier to look at. It's longer but ultimately faster.

[Anonymous No.7042563]

>>7042439
I would say I am average at mental math and I can do both of those in my head in about 15-20 secs. 2.5 minute is a long time.

[Anonymous No.7042643]

>>7042439
It developed over years of math.

I do 19894 + 741 mentally in my head.
I can hold all the numbers visually and go through it in a few seconds

At some point it just becomes natural.

Though algebra is WAY easier than arithmetic. Can calculus is easier than algebra.

[Anonymous No.7042645]

It developed over years of math.

I do 19894 + 741 mentally in my head.
I can hold all the numbers visually and go through it in a few seconds

At some point it just becomes natural.

Though algebra is WAY easier than arithmetic. And calculus is easier than algebra.

[Anonymous No.7042668]

I'm actually really bad at it. seems like a thing for circus rather then a skill.

[Anonymous No.7042725]

>>7042439
1st one about 10-12 seconds.
2nd one 6-7 seconds.

2.5 minutes is absurd.

[Anonymous No.7043113]

>>7042725
Yeah, my b.

I just went with a time limit I thought everyone could do.

[Anonymous No.7043938]

>>7042439
Stuff like this is practically useless. Nobody will give you numbers like this in a class and outside of a class you'll have a calculator. This is only useful to impress elementary level kids in a math club.

[Anonymous No.7043957]

>>7043938
Decent mental arithmetic is very useful for doing proofs.

You're literally a retard if you can't do the stuff in the OP in a few secs.

[Anonymous No.7043965]

this is retarded

>>24 * 36
>24 * 30 = 720
>24 * 6 = 144
>720 + 144 = 864

>>19894 + 741
>19894 + 6 + 735
>19900 + 735
>20635

[Anonymous No.7043971]

>>7042439
I was a waiter for a while.
So yeah, when it comes to grade school arithmetic in my head I have it. It's a simple skill anyone can attain.

[Anonymous No.7043988]

>>7043938
No.
It's a useful skill and a fun game.

[Anonymous No.7043994]

Or. Or. Or. You could use a calculator.

>>7043957
No, solving proofs is very useful for solving proofs. Any time spent with this savant bullshit is time could have been spent learning.

>>7043988
It's entirely useless. It's a party trick and the equivalent to memorizing a million digits of pi. If it's fun to you then whatever; I hear some people find Angry Birds pretty fun.

[Anonymous No.7043999]

>>7042439
>under 2 and a half minutes
wtf?
24 * 36 = 25*36-36 = 100*36/4-36=90-36=60-6=54

[Anonymous No.7044004]

>under 2 and a half minutes
wtf?
24 * 36 = 25*36-36 = 100*36/4-36=900-36=864