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Multiplying A 2-digit Number By 87

Multiplying A 2-digit Number By 87

Multiplying a 2-digit number by 87

  1. Select a 2-digit number.
  2. Multiply it by 9.
  3. Add one zero.
  4. Subtract three times the original number.
   Example:
  1. The 2-digit number chosen to multiply by 87 is 21.
  2. Multiply by 9: 9 × 21 = 189.
  3. Add one zero: 1890.
  4. Subtract three times the original number: 1890 - 3(21) = 1890 - 60 - 3 = 1830 - 3 = 1827.
  5. So 87 × 21 = 1827.

   See the pattern?

  1. Next selection is 52.
  2. Multiply by 9: 9 × 52 = 450 + 18 = 468.
  3. Add one zero: 4680.
  4. Subtract three times the original number: 4680 - 3(52) = 4680 - 150 - 6 = 4530 - 6 = 4524.
  5. So 87 × 52 is 4524.

 

Review subtracting and multiplying left to right and these answers should come easily.




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26 Sep, 2021, 03:05:09 AM