Jagoan Matematika: Squaring numbers in the 50s

Jagoan Matematika

Gateway For Tour Brain Math

Sunday, May 20, 2007

Squaring numbers in the 50s

1. Square the last digit (keep the carry) _ _ _ X
2. Multiply the last digit by 10, add the carry _ _ X _
3. The first digits will be 25 plus the carry: X X _ _

Example:

1. If the number to be squared is 53:
2. Square the last digit (keep the carry): 3 × 3 = 9 (keep 3) _ _ _ 9
3. Multiply the last digit by 10, add the carry: 10 × 3 = 30 (keep 3) _ _ 0 _
4. The first digits will be 25 plus the carry: 25 (+ carry): 25 + 3 = 28 2 8 _ _
5. So 53 × 53 = 2809.

See the pattern?

1. If the number to be squared is 56:
2. Square the last digit (keep the carry): 6 × 6 = 36 (keep 3) _ _ _ 6
3. Multiply the last digit by 10, add the carry: 10 × 6 = 60, 60 + 3 = 63 _ _ 3 _
4. The first digits will be 25 plus the carry: 25 (+ carry): 25 + 6 = 31 3 1 _ _
5. So 53 × 53 = 3136.

Practice and you will soon be producing these products quickly and accurately.

posted by marhadi @ 6:42 AM

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