So, the definition of a square root is "what number can be multiplied by itself in order to yield the given number". So, if we apply this theory, what number can be multiplied by itself so that it gives an answer of 100.
So, the factors of 100 are
1 * 100
2 * 50
4 * 25
5 * 20
10 * 10 -> See, this one, 10 is being multiplied by 10. So, that is the square root of 100.
