Thread: Puzzles for you
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Old 05-24-2006, 01:26 PM
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Thanks indianbaba for making this thread sticky. It would surely help others.

Finger Multiplication
by Sidney Kolpas
Mathematics Teacher April 2002


It requires that the students hold both hands up, with palms facing the student. The student counts his or her thumbs and fingers consecutively
from left to right, with the thumb on the left hand representing the number 1 and the thumb on the right hand representing the number 10. To multiply n times 9, where 1 <= n <= 10 and where n is a whole number, the student bends down the nth finger. The number of fingers to the left of the bent finger represents the tens-place digit of the product, whereas the number of fingers to the right of the bent finger represents the ones-place digit of the product.

The figure below illustrates 7 x 9.





Mr. Kolpas explains why this works in his article in the April 2002 issue of the Mathematics Teacher.
Courtesy : http://www.pen.k12.va.us
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