Trick 25 : Squaring a 2-digit number beginning with 5

Squaring a 2-digit number beginning with 5
Take a 2-digit number beginning with 5.

Square the first digit.

Add this number to the second number to find the first part of the answer.

Square the second digit: this is the last part of the answer.

Example:

If the number is 58, multiply 5 × 5 = 25 (square the first digit).

25 + 8 = 33 (25 plus second digit).

The first part of the answer is 33 3 3 _ _

8 × 8 = 64 (square second digit).

The last part of the answer is 64 _ _ 6 4

So 58 × 58 = 3364.



See the pattern?

For 53 × 53, multiply 5 × 5 = 25 (square the first digit).

25 + 3 = 28 (25 plus second digit).

The first part of the answer is 28 2 8 _ _

3 × 3 = 9 (square second digit).

The last part of the answer is 09 _ _ 0 9

So 53 × 53 = 2809.