6 is the answer.
Explanation:
6 because the square root of 45 averages to about 6.70 and we know that in order for a number to be an integer, that it has to be a whole number. So, if we round it back to figure out what whole number is less than 6.70, since the integer has to be less than the square root of 45, then we will get 6 as the answer.
