Math Fun Facts

Squares of a Number Ending in 5

There's a quick way to do this: if the first digit is N and the second digit is 5, then the last 2 digits of the answer will be 25, and the preceding digits will be N*(N+1)

For instance 

205² = 42025, since (20*21)25 = (420)25-- 42025

45² = 2025,    since (4*5)25= (20)25 -- 2025
85² = 7225,    since (8*9)25= (72)25-- 7225

Hope this helps...