Well, just by looking at the beginning of the problem, Jamelia had made the common mistake of thinking that
[tex] \sqrt{72}[/tex] (8.4852...)
is equal to
[tex]2* \sqrt{36} [/tex] (12)
If you want to estimate a square root like 72, simply find squares that would fit around the number you are looking to find, in our case, 72.
So 9*9 is 81, which is too high and 8*8 is 64, which is too low. So you know that somewhere between those numbers is what your root of 72 is!