Squaring numbers in 20s

Squaring numbers in the 20s

1. Square the last digit (keep the carry) _ _ X
2. Multiply the last digit by 4, add the carry _ X _
3. The first digit will be 4 plus the carry: X _ _

Example:

If the number to be squared is 24:

1. Square the last digit (keep the carry):
   4 × 4 = 16 (keep 1) _ _ 6
2. Multiply the last digit by 4, add the carry:
   4 × 4 = 16, 16 + 1 = 17 _ 7 _
3. The first digit will be 4 plus the carry:
   4 (+ carry): 4 + 1 = 5 5 _ _
4. So 24 × 24 = 576.