The square root of 324 is 18. The square root of a number can also be a negative number because the square of a negative number is always a positive number. The equation (-18) x (-18) = 324, therefore, the square root of 324 can also be (-18).
The square root of a number is determined by obtaining the factors of the number. The factors of 324 are 2 x 2 x 3 x 3 x 3 x 3; these factors can be simplified to show 2 x 3 x 3 squared, which is 18 x 18 = 324.
Similarly, the square root of 400 is either 20 or (-20). Numbers that are perfect squares have exact square roots. If a number is not a perfect square, its square root is a decimal fraction.