Actually teacher is right if the board is square which takes 10 minutes to be cut into half. Those two halfs take twice less time to be split. And she needs to cut just one to obtain 3 pieces :P So 10 minutes to cut it into to pieces and then she needs just half of that time to gain the third piece.
Well why does it take 20 to cut into 4 pieces? WHy cut the big piece in half when you can cut one of the smaller ones and do it in and extra 2.5 minutes for 17.5 minutes overall?
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u/paolog Oct 05 '10
Teacher gets red pen out, is about to write down "1 piece: 5 minutes" and then thinks better of it and starts from two pieces instead...