Matematika Tips and Trick: Squaring a 2-digit number beginning with 1 (mengkuadratkan puluhan dengan bilangan pertamanya 1)

Matematika Tips and Trick

Monday, March 05, 2007

Squaring a 2-digit number beginning with 1 (mengkuadratkan puluhan dengan bilangan pertamanya 1)

Take a 2-digit number beginning with 1.
Square the second digit
(keep the carry) _ _ X
Multiply the second digit by 2 and
add the carry (keep the carry) _ X _
The first digit is one
(plus the carry) X _ _
Example:
If the number is 16, square the second digit:
6 × 6 = 36 _ _ 6
Multiply the second digit by 2 and
add the carry: 2 × 6 + 3 = 15 _ 5 _
The first digit is one plus the carry:
1 + 1 = 2 2 _ _
So 16 × 16 = 256.
See the pattern?

For 19 × 19, square the second digit:
9 × 9 = 81 _ _ 1
Multiply the second digit by 2 and
add the carry: 2 × 9 + 8 = 26 _ 6 _
The first digit is one plus the carry:
1 + 2 = 3 3 _ _
So 19 × 19 = 361.

posted by neneng sriwiyanti @ 8:44 PM

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