Squaring 2-Digit Numbers That End In 5
Example:
35
x35
The answer will end in 25 (because 5x5=25) so write that down.
Then, look at the tens digit (3). Multiply that number by the number that is one greater than it: 4
Write that answer in front of the 25.
So your answer will be 1,225
It works for squaring any 2-digit number that ends in 5.