Put ten sugar lumps in three cups so every cup holds an odd number
A dinner guest challenges the table: place ten lumps of sugar into three teacups so that each of the three cups contains an odd number of lumps. A young law student insisted it was impossible. Can you find the trick?
Reveal the answer
Put one lump in a small cup, then set that cup inside a second cup holding two more lumps — the second cup now 'contains' three lumps in total, an odd number. Put the remaining seven lumps in the third cup. All three cups legitimately hold an odd count, because a cup that holds another cup holds its contents too.
— Henry Dudeney, The Canterbury Puzzles — Puzzle 55, 1907
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