BEATCALC:  Beat the Calculator!

___________________________________________
Back to Calculation Tips & Tricks
___________________________________________

From the BEATCALC mailing list:
a weekly service from B. Lee Clay, archived here by the Math Forum.
To subscribe to the BEATCALC mailing list, write to BEATCALC@aol.com.


   Multiplying a 2-digit number by 8 1/3

  1. Select a 2-digit number.
  2. Add two zeros.
  3. Divide by four.
  4. Divide by three.

   Example:

  1. The 2-digit number chosen to multiply by 8 1/3 is 64.
  2. Add two zeros: 6400.
  3. Divide by four: 6400/4 = 1600.
  4. Divide by three: 1600/3 = 555 1/3.
  5. So 64 x 8 1/3 = 555 1/3.

   See the pattern?

  1. The 2-digit number chosen to multiply by 8 1/3 is 37.
  2. Add two zeros: 3700.
  3. Divide by four: 3700/4 = 925.
  4. Divide by three: 925/3 = 308 1/3.
  5. So 37 x 8 1/3 = 308 1/3.


webmaster@forum.swarthmore.edu
17 April 2000
Web page design by Sarah Seastone