In this tutorial, we will learn how to obtain a square of a number ending in 25. For example, numbers such as 25, 125, 325, 425 etc. You already know the shortcut, how to multiply any number ending with 5. You can use the same shortcut here as well.
However, if the number is big, the shortcut might take more time. In this shortcut, I will explain, how to obtain the square ending with 25.
Let’s say, we want to calculate the square of 1252. The entire steps are illustrated in the following figure.
Step 1 : Break the number such that 25 is on the right and the rest of the digits ( i.e, 1 in this case) is on the left.
Step 2 : Obtain the square of 25 which is 625. This forms the second (RHS) part of the answer.
Step 3 : Take the rest of the digit on the left (1) and append 5 to this digit and multiply by the digit on the left to get the L.H.S part of the answer.
So, the final answer is 625.
Let’s take another example to make it clear. Can you guess, what is the square of 5252 ?
Similarly, 16252 would be ?
Notice the multiplication 165 x 16. Even though it looks very difficult in the beginning, if you have practiced the multiplication shortcuts, you can obtain the answer very easily.
If you to master these shortcuts, you have to be good with basic multiplication. The shortcut for multiplying any 2 numbers using criss-cross method of multiplication can be found here.
Exercise : can you mentally calculate?
If you have any doubts related to this tutorial, please leave a comment. I would be glad to help.