short method is the shortcut method of something like addition , subtraction , ETC
Example:
*in addition we will add the #s w/ the sum is a multiple of 10
28+13+2+7=?
(we will add 28 and 2 because their sum is 30 which is a multiple of 10)
(then we will add 13 and 7 because their sum is 20 which is a multiple of 10)
SO.....it will be:(from 28+13+2+7 it will then be like this:)
30+20=50
