BEATCALC:  Beat the Calculator!

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Back to Calculation Tips & Tricks
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From the BEATCALC mailing list:
a weekly service from B. Lee Clay, archived here by the Math Forum.
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   Multiplying a 2-digit number by 35

  1. Select a 2-digit number.
  2. Multiply it by 7.
  3. Divide by 2.
  4. Add a zero.

   Example:

  1. The 2-digit number chosen to multiply by 35 is 28.
  2. 7 x 28 = 140 + 56 = 196.
  3. Divide by 2: 196/2 = 98.
  4. Add one zero: 980.
  5. So 35 x 28 = 980.

   See the pattern?

  1. The 2-digit number chosen to multiply by 35 is 68.
  2. 7 x 68 = 420 + 56 = 476.
  3. Divide by 2: 476/2 = 238.
  4. Add one zero: 2380.
  5. So 35 x 68 = 2380.

Practice and you will be able to give these products easily and accurately.


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7 September 1998
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