High School Math

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Thursday, June 22, 2006

Magic Number

Write down any 3-digit number. (Let's say, 276)
Write it down again beside itself. (This means 276276)
Divide that result by 7. (Answer is 39468)
Divide that result by 11. (Answer is 3588)
Divide that result by 13. (Answer is 276, the original number)
Why does this happen?
Writing a 3-digit number beside itself is equivalent to multiplying it by 1001 because 1001 = 7 x 11 x 13. So, all that is being done by dividing the large number by 7, 11 and 13, is to return it to the original 3-digit number.

More Magic at www.TheMathWebSite.com.