On square roots, always look at the units digit. Observe the pattern
1^2 ends in 1.
2^2 ends in 4.
3^2 ends in 9.
4^2 ends in 6.
5^2 ends in 5.
6^2 ends in 6.
7^2 ends in 9.
8^2 ends in 4.
9^2 ends in 1.
0^2 ends in 1.
Also, when you have (x5)^2, where x5 is a two digit number in the form of 10x+5, find (x)(x+1), then add 25 at the end.
For example, 25^2. In this case, x is 2. So, 2*3=6. Then add the 25 at the end to get 625.
Square roots are vice versa.
