Question

The sum of the two digits of a certain two-digit number equals the square root of the number? What is the number?

Answer 1

81

Explanation:

2-digit squares are 16, 25, 36, 49, 64, 81.

Their sums of digits, are ...

7, 7, 9, 13, 10, 9

The square 81 has a sum of digits equal to its square root.