median
don steward
mathematics teaching 10 ~ 16

Saturday 12 February 2011

deletions

choose any number (circle it) and cross out the other numbers in the same row and column as this
then do this again
and do it a third time
then put a circle round the remaining number and add up the four numbers

do this a couple of times
what happens?
why does it happen?

[ idea from Mathematics in School, January 1989 ]

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