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## 'Farmers Field' printed from http://nrich.maths.org/

A farmer has a flat field and two sons who will each inherit
half of the field. The farmer wishes to build a stone wall to
divide the field in two so each son inherits the same area. Stone
walls are expensive to build, so naturally the farmer wishes to
build the shortest wall he can.

Can you prove that the shortest wall is always straight,
whatever the shape of the original field? Or perhaps you can find a
shape where the shortest wall isn't straight!