1: the square root of 1 is one.
4: the square root of 4 is 2.
9: the square root of 9 is 3.
25: the square root of 25 is 5.
36: the square root of 36 is 6.
81: the square root of 81 is 9.
144: the square root of 144 is 12.
225: the square of 225 is 15.
400: the square root of 400 is 20.
