Jagoan Matematika: Squaring numbers in the 30s

Jagoan Matematika

Gateway For Tour Brain Math

Sunday, May 20, 2007

Squaring numbers in the 30s

1. Square the last digit (keep the carry) _ _ _ X
2. Multiply the last digit by 6, add the carry _ _ X _
3. The first digits will be 9 plus the carry: X X _ _

Example:

1. If the number to be squared is 34:
2. Square the last digit (keep the carry): 4 × 4 = 16 (keep 1) _ _ _ 6
3. Multiply the last digit by 6, add the carry: 6 × 4 = 24, 24 + 1 = 25 _ _ 5 _
4. The first digits will be 4 plus the carry: 9 (+ carry): 9 + 2 = 11 1 1 _ _
5. So 34 × 34 = 1156.

See the pattern?

1. If the number to be squared is 36:
2. Square the last digit (keep the carry): 6 × 6 = 36 (keep 3) _ _ _ 6
3. Multiply the last digit by 6, add the carry: 6 × 6 = 36, 36 + 3 = 39 (keep 3) _ _ 9 _
4. The first digits will be 9 plus the carry: 9 (+ carry): 9 + 3 = 12 1 2 _ _.
5. So 36 × 36 = 1296.

With some practice you will be giving these squares quickly.

posted by marhadi @ 6:38 AM

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