Question

Is 20 a perfect square number?

Answer 1

No. It's root is `4.4721...`

Explanation:

You could have seen this without calculating in two ways:

`4^2=16` which is too low
`5^2=25` which is too high.

Or:
A square allways ends in an even number of zeroes. Every zero at the end means a factor 10, and in squares every factor is paired.