If you need to square a 2 digit number ending in 5, you can do so very easily with this trick. Multiply the first digit by (itself + 1), and then just put 25 in the end. That’s all!

Let’s take an example of 25^2

Here first digit is 2. Add 1 to 2 which is 3. 2 times 3 is 6. Now put 25 at the end, hence the answer is 625; that is, 2 * (2+1)…25 = 625

Let’s understand with another example, 45^2 = 4*(4+1)…25 = 2025