kitchen table math, the sequel: long division & mental math

Sunday, July 12, 2009

long division & mental math

Barry Garelick:
Investigations and EM both boast about how their programs emphasize mental math. Though they don't seem receptive to the idea of teaching long division. I wonder why not? Long division is an ideal way to hone mental math skills. A problem like 56,098 divided by 84 requires a lot in the way of number sense and mental math. The first step is looking at the maximum number you can have to multiply by 84 and stay under 560. Rounding, 560 divided by 80 would be 7, but a quick glance will tell you that 7 x 84 will be greater than 560, which quickly leads you to "6" for a choice. And so on and so forth. But reformers don't want to hear about all that. It's drill and kill, has no value, and anyway, calculators have made long division obsolete.

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