Determining whether a number is a perfect square is not as hard as it might at
first seem. For instance, suppose we wanted to know whether the number 648 is
a perfect square. Do you see why the square root of 648 must be between 20 and
30? Can you think of an easy way to check whether 648 can possibly be a perfect
square? [Hint: Think about the possible final digit a perfect square can have.] Is
648 a perfect square?