World's Worst Riddles

A friend purchased "The World's Worst Riddles", a slim book at a second-hand bookshop.


Published in 1968, its Introduction says that by "worst", it might mean "best".


However... here are some for mathematicians:


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Q: A man bought 90 hens. He placed 30 on the first perch, 30 on the second, and the remaining 30 on the top perch. How many hens did he own?
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A: Only the ones on the first perch because the others were on higher perches (hire purchase).


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Q: If it took eight men eight hours to build a brick fence how long would it take five men to build it?
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*A: None, because the eight men have done the work.


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Q: If six magpies are sitting on a fence and one is shot, how many are left?

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A: None, because the others flew away.


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Q: Two's company, three's a crowd but what is four and five?

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A: Nine.