Square root perfect square – UGC NET Question

This option is correct because the square root of a number is a value which, when squared, gives the original number. Here, 9 × 9 = 81. The positive value that satisfies this is 9. Therefore, the positive square root of 81 is 9.

Option A:
If we square 7, we get 49, which is less than 81. Thus, 7 is not the square root of 81. It does not satisfy the required condition.

Option B:
Squaring 8 gives 64, which is still less than 81. Hence, 8 is not the number whose square equals 81 and cannot be the correct answer.

Option C:
The number 9 squared gives exactly 81, so 9 is the positive square root of 81. The question asks specifically for the positive square root, so we choose 9 and not −9. Therefore, this option is correct.

Option D:
81 is the original number itself and would be the square of 9, not its square root. Squaring 81 gives a much larger number, 6561. Thus, 81 cannot be the square root of 81.