don steward
mathematics teaching 10 ~ 16

Saturday, 8 January 2011


practice in subtracting two, 3-digit numbers
form a three digit number with the last two digits summing to the first
e.g. 615
rotate the digits one place (front goes to the back) and subtract
i.e. 615 - 156
which is 459
divide the result by 9 (it always will)

what pattern do you notice in the result?
try to explain this pattern

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