I know there's a trick to square something in your head, is there a trick to cube something?

Question

the trick for squaring something is like square the first, square the second, twice the middle number

is there a trick for cubing something...say (a+h)^3

can someone show me step by step how to do (a+h) ^3?

Answer 1

Hehehe. There's a couple answers to the first question. The 'trick' (if it can be called that) is to remember the Binomial Theorem. And the easy way to remember that is Pascals Triangle. (Look up Pascals Triangle on the Web to see how to get the coefficients of a binomial raised to a power)

There is also a cute trick to allow you to square a numerical value up to 100 in your head. It depends on the identity
(a + b)(a - b) = a² - b².
If yu want to square a, just choose an 'intelligent' value for b such that either a + b or a - b is an exact multiple of 10. For example:
63² = (63 + 3)*(63 - 3) + 3²
63² = 66*60 + 9 = (66*6)*10 + 9 = 396*10 + 9 = 3969
The b will always be between 0 and 5 so it's easy to square, and the other multiplication is easy since it's -always- a multiple of 10.

Doug

Answer 2

square it first ten multiply it by the original number you are cubeing