What is a perfect square between 81 and 121

100 is the answer because it is the only number between 81 and 121

Let's set it up to make it easier:

81 = 9

? = ?

121 = 11.

When taking note of perfect squares and their roots, they tend to be written in numeric order (1,2,3 ...). We know that the number 10 is in between 9 and 11, so we need to find out the square of 10.

10^2 (or 10*10) = 100. 100 = 10.