Math Trick 1: Squaring Numbers Ending in 5

Math tricks and mental math shortcuts are used to perform speedy calculations. Many of us know at least a trick or two because they are easy to remember and handy to use. But why or how do these tricks work?

This is the first of a series of posts that will discuss math tricks and mental math shortcuts. Aside from the algorithm that will be taught in this series that will benefit everyone, we will also investigate why they work.

The Trick: Squaring Numbers Ending in 5

Squaring numbers ending in 5 is probably the most popular among the math tricks and mental shortcuts. Below is the algorithm of the trick.

Math Trick Squaring Numbers Ending in 5


  1. Take 25 as the last two digits of the product of the factors.
  2. Add 1 to the tens digit of one of the factors.
  3. Take away 5 from both the factors, and multiply the remaining numbers.
  4. Append the product in the third step to the left of the result in the first step. » Read more