Square root of 3969

How to get square root of 3969 without calculator
Please explain

As a first attempt, you don't know whether it's a perfect square or not. Check it's factors:

3969 = 3 * 1323 = 3 * 3 * 441 = 3 * 3 * 3 * 147 = 3 * 3 * 3 * 3 * 49 = 3 * 3 * 3 * 3 * 7 * 7

Since there you can group them in pairs, 3969 is a perfect square. Now, group the pairs of similar factors together, and remove one from each pair, giving 3 * 3 * 7 = 9 * 7 = 63.

So, 63 is the square root of 3969.

That is one method.