Sender: Noria
Subject: re :chismbop math
Date: Sun, 26 Apr 1998

Dear Sir/Madame:

About a year ago a grade 5 teacher at my son's school taught the children how to multiply the 9 times table on their fingers quickly.

It was part of a kind of finger math kind of thing. It allows quick calculation on their fingers. I have to no avail checked libraries etc. and come up empty handed. I am very much interested in learning more about this so as to teach it to my children and their classmates. If anyone can direct to any information re chismbop math. I would greatly appreciate it. Thankyou.

Your interest and response is greatly appreciated.


Here it goes:

Hold up both hands in front of you, fingers apart, palms facing away from you. Now bend over the finger that you want to multiply nine by, counting fingers from left to right. For example, to multiple nine by six, bend over the thumb on your right hand (the sixth finger).

Count the number of fingers to the left of the bent finger. This is your 10s positition. Count the number of fingers to the right of the bent finger. This is your 1s position. If you bend over the sixth finger, you have five fingers to the left and four fingers to the right of the thumb. Hence 9*6=54.

Two suggestions, which might make this method interesting for older students:

The method works for any base-n, multiplying by "n-1". To multiply a number by 7 in base-8, draw an eight fingered "alien" and bend over the appropriate finger.

It also works with multipliers greater than 10. There are some restrictions, and you have to reserve fingers for the 100s position, but it is possible with some numbers.

Hope this helps....


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