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Figure This!


Complete Solution:

Most household wrenches will not work on the valves of a fire hydrant because there are no parallel sides on the five-sided (pentagonal) valve

All of the angles of a valve on top of a fire hydrant are the same size. The five sides have equal length. (The valve top is a regular pentagon.) No five-sided figure with these characteristics can have parallel sides.

This means that an ordinary household wrench will not fit. This design makes opening hydrants difficult without the special wrenches carried by firefighters.

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