Interesting post on allowing kids to use fingers to count. I never quite understood the opposition in the first place.
Hidden near the end is an interesting technique for multiplying by 6, 7, 8, 9, or 10.
To multiply 8 by 7, say:
Algorithm:
1. Touch the "8" and "7" fingers
2. The number of fingers including the touching fingers (5, here) forms the tens place (5 * 10 = 50)
3. Multiply the number of fingers remaining on either hand (3 * 2 = 6)
4. Sum step 2 and 3 (50 + 6 = 56).
Can you figure out why this technique works?
Hidden near the end is an interesting technique for multiplying by 6, 7, 8, 9, or 10.
To multiply 8 by 7, say:
Algorithm:
1. Touch the "8" and "7" fingers
2. The number of fingers including the touching fingers (5, here) forms the tens place (5 * 10 = 50)
3. Multiply the number of fingers remaining on either hand (3 * 2 = 6)
4. Sum step 2 and 3 (50 + 6 = 56).
Can you figure out why this technique works?
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