How to calculate the square root of a number that not included in the square numbers

Today, I'll share about 'Square Root'. Maybe, many people who doesn't know how to count square root if nothing number that squared will have result as same as wanted. I will share to all of world people, particularly my friends in class 8J - JHS 2 Taman Sidoarjo, East Java, Indonesia.

Well, the squared numbers are:
1 = 1 x 1
4 = 2 x 2
9 = 3 x 3
16 = 4 x 4
25 = 5 x 5, and so.

If we are meet a problem in a book or it's given by our teacher, but the problem is written (simple):

1. What is square root of 245?

Then, the problem solving for number 1 is:
245 is between 225 (square of 15) and 256 (square of 16)
So, square root for 245 = 15,...


To find above dots:
Number which sought for square root (245) minus with the lower square number (225) then divided by the higher square number (256) minus with the lower square number (225)
Number result:
= (245 - 225) / (256 - 225)
= 20 / 31

So, the result is 15 20/31 = 15,65

If you use calculator, you'll find the next number after 15,65 :)
But we will find the exact number without use more times :)