# Square of a number which is above 25 and below 75 by using 25-50 rule

Lets say, we want to calculate the square of 39. The entire steps are illustrated in the following figure.

Step 1: On 25, given number 39 is 14 more. This is the 1st part of the answer.

Step 2: On 50, given number 39 is 11 less. Find the square of 11, the result is 1/21. We need to have only two digit number. If it is a 3- digit number left most digit is added to 1st part. The 2- digit number (21) is the 2nd part of the answer.

The final answer is 1521

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