## BEATCALC:  Beat the Calculator!

Back to Calculation Tips & Tricks

 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

Subtracting Numbers

Finding Percents

Calculation
Practice Exercises

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### Multiplying a 2-digit number by 36

1. Select a 2-digit number.
2. Multiply it by 4.
4. Subtract the number obtained by multiplying by 4 from the last number.

#### Example:

1. The 2-digit number chosen to multiply by 36 is 52.
2. 4 × 52 = 208 (multiply by 4).
4. 2080 - 208 = 1872
(Subtract left to right in steps:
2080 - 200 - 8 = 1880 - 8 = 1872)
5. So 52 × 36 = 1872.

See the pattern?

1. If the number to be multiplied by 36 is 86:
2. 4 × 86 = 344 (multiply by 4):
(Think 4 × 86 = (4 × 80) + (4 × 6) = 320 + 24 = 344.)
4. 3440 - 344 = 3096
(Subtract left to right in steps:
3440 - 300 - 40 - 4= 3140 - 40 - 4 = 3100 - 4 = 3096)
5. So 86 × 36 = 3096.

Mastering the subtraction from left to right will enable you to produce these products of 36 and 2-digit numbers quickly and accurately.