Mental math

[T_FLeX]

It seems as though everyone has different ways of doing simple calculations in their head, like adding multiplying, dividing. I was just wondering if any of you guys have a good method of doing this, I have been trying to decide which is the most efficient; maybe you guys can help me out.

When I come across simple addition, lets say 37 + 17 I first break down the two numbers into multiples of 5, so I would figure 35+15 real quick then take the remaining numbers and add them, then add the two sums together so for me it's like 50+4=54 I can do this pretty fast but sometimes people can calculate things much faster. I also have a method for subtracting, that I will admit to be somewhat confusing and usually ends up slowing me down, but I have found it extremely hard to break the habits, because I have been doing them all my life.

This is the way I have always done it, I'm just curious, if this is the way you guys do it? Does anyone have a method that works particularly well for you?

[dave]

my own personal method when it comes to mental math additions is to break it down into tens and units. so if i had 42 + 12 i'd say it's 42 + 10 + 2 (obviously not for something that simple). this way generally works best for me. i can kindof do the same thing for subtraction and multiplication. i'm not very good at division, however.

apparently (or so i've been told), kids who are trained using abaci (i mean really trained like hell, hours per day) have amazing mental math capabilities, doing stuff like 1531 * 1084 in their heads. it comes from a basic understanding of the way numbers work.

[blike]

apparently (or so i've been told), kids who are trained using abaci (i mean really trained like hell, hours per day) have amazing mental math capabilities, doing stuff like 1531 * 1084 in their heads. it comes from a basic understanding of the way numbers work.

In the 1800s children could divide and multiply numbers in their head like that. amazing eh? Just goes to show what a little discipline will do for your brain.

But yea, I do it the same way dave does, break it down to the nearest unit of ten (for addition and subtraction anyway). For anything more, out comes the TI ;)

To be honest, I probably use the TI to do my addition. we're spoiled rotten with these things. :cool:

[fafalone]

It enables us to focus our abilities on more complex tasks, and also allows us to perform complex tasks quicker.

The children of the 1800s may have been able to do complicated arithmetic in their head, but they sure couldn't compute the definite integral of an irrational function.

[Dudde]

right, for addition and subtraction I round the numbers to the nearest ten and add the ones up and add them all together:D