Mathematical Mondays 9-6-10

I like 11 times tables. Not only because 1-9 were so easy, but even higher ones can be fun.

Two digit numbers, for example, when you multiply them by 11, you split the two digits apart, then add them for the middle digit to get the answer. For example: 34*11 = 374 or 62*11 = 682. If the middle number is greater than 9, just add the 1 to the digit on the left (in the 100’s spot). 68*11 = 748 or 93*11 = 1023.

More fun with 11’s, multiply 11 by any lineup of digits with zeros between them to get a line-up of pairs of digits: 102030405*11 = 1122334455

Also, any number that’s a palindrome with an even number of digits is divisible by 11. 314413/11 = 28583 or 385726627583/11 = 35066057053

In conclusion. 11’s are fun. Thanks. Enjoy your labor day!

1 Comment (+add yours?)

  1. Eleni
    Sep 07, 2010 @ 03:20:01

    Ooo, I never realized that about the double digits x 11. I love little math tricks like that.


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