Squaring numbers in your head
Walter Hickey / BI
Squaring large numbers can be a real pain sometimes. But if you're plugging something into a formula, easy mental squaring could be a huge asset.
So say you've got a number, x, that you want to square.
Find "d" the difference between the nearest multiple of ten and x.
Then, multiply (x-d) and (x+d). This should be much easier, because one of the numbers is a multiple of ten. Just add d2, and you've got your square.
Here's an example. I want to find the square of 84. The nearest multiple of ten is 80, so d is 4.
x+d is 88, x-d is 80.
88 X 80 = 6400 + 640 = 7040. Add 42 = 16, and you get 7056.
That process, once you get the hang of it, is much easier than just attacking 842 head on.
Read more: http://www.businessinsider.com/x-math-party-tricks-that-will-make-you-a-rockstar-2013-6?op=1
Walter Hickey / BI
Squaring large numbers can be a real pain sometimes. But if you're plugging something into a formula, easy mental squaring could be a huge asset.
So say you've got a number, x, that you want to square.
Find "d" the difference between the nearest multiple of ten and x.
Then, multiply (x-d) and (x+d). This should be much easier, because one of the numbers is a multiple of ten. Just add d2, and you've got your square.
Here's an example. I want to find the square of 84. The nearest multiple of ten is 80, so d is 4.
x+d is 88, x-d is 80.
88 X 80 = 6400 + 640 = 7040. Add 42 = 16, and you get 7056.
That process, once you get the hang of it, is much easier than just attacking 842 head on.
Read more: http://www.businessinsider.com/x-math-party-tricks-that-will-make-you-a-rockstar-2013-6?op=1
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