Answer
4
Explanation
The square root of a number always gives two results. One negative and the other one positive.
√16 = -4 also √16 = +4.
This is true because,
(-4)² = 16 and
(+4)² = 16.
When we are looking for the square root if a positive number we are actually interested with the positive root. This is the one referred to as principal square root.
∴ The principal square root of 16 is 4.
