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 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

Subtracting Numbers

Finding Percents

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Multiplying a 2-digit number by 22

1. Select a 2-digit number.
2. Multiply it by 2.
3. The last digit will be the same.   _ _ _ X
4. Add the digits right to left.

Example:

1. The 2-digit number chosen to multiply by 22 is 78.
2. 78 × 2 = 156 (multiply by 2).
3. Last digit is 6.   _ _ _ 6
4. Add digits right to left. 6 + 5 = 11   _ _ 1 _
5 + 1 + 1 (carry) = 7   _ 7 _ _
5. The first digit is the same.   1 _ _ _
6. So 22 × 78 = 1716.

See the pattern?

1. The 2-digit number chosen to multiply by 22 is 34.
2. 34 × 2 = 68 (multiply by 2).
3. Last digit is 8.   _ _ 8
4. Add digits right to left. 8 + 6 = 14   _ 4 _
5. First digit + carry: 6 + 1 = 7   7 _ _
6. So 22 × 34 = 748.

Practice getting products by adding digits right to left. Then you will be able to multiply by 22 in your head with ease.