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

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

https://www.hamaraguru.com/assets/files/2018-01-12/1515745633-990161-imgur-26.jpeg
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

One more Example:
https://www.hamaraguru.com/assets/files/2018-01-12/1515747384-211758-imgur-27.jpeg