Question

If a square has an area of 81 square how long is each side ?

Answer 1

The area of a square is

       (length of a side) times (length of a side) .

So if you want to know the length of the side,
you have to find a number that gives you 81
when you multiply the number by itself.

That's called the "square root" of 81 .

Each side of your square is 9 units long.