Squaring Any Two-Digit Number Whose Tens Digit IS 5

Rule: Add the units digit to 25 and affix the square of the units digit to the result. If the square of the units digit is a one-digit number, precede it with a 0.

Find the square of 53, using this method.

First, add the units digit, 3 to 25.

        25 + 3 = 28

Next, affix the square of the units digit to the result.

        3 X 3 = 9

Since the answer is a one-digit number, place a zero in front of 9 before affixing it to the 28.

          2,809 Answer

As another example, find the square of 57.
Again, the units digit is added to 25.

        25 + 7 = 32

Next,square the units digit

        7 X 7 = 49

and affix to the previous result.

        3,249 Answer

This time the square of the units digit was a two-digit number, and therefore it was not necessary to precede it with a zero.