Learn all about logarithms. The logarithm of a number say a to the base of another number say b is a number say n which when raised as a power of b gives a. (i.e. log [base b] (a) = n means that b^n = ...

You may find this hard to believe, but there are people still alive today who once did their mathematical calculations by sliding sticks back and forth. No keypads, no batteries, no LEDs. Just sticks.