Multiplication tricks, part one of many

Squaring a two-digit number ending in 5

The last two digits will always be 25.

To get the first digit(s), take the tens digit of your number and multiply it by the next integer.

Example: 45²

To get the first two digits, multiply 4 by 5 (the next consecutive integer) to get 20. Last two digits are 25. So

45² = 2025.