Thirteen commercial travellers arrived at an inn, and each desired a
separate room. The landlady had but 12 vacant rooms, which may be
represented thus:--
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| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
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But she promised to accommodate all according to their wishes. So she
showed two of the travellers into room No. 1, asking them to remain a
few minutes together. Traveller No. 3 she showed into room No. 2,
traveller No. 4 she showed into room No. 3, traveller No. 5 into room
No. 4, traveller No. 6 into room No. 5, and so on until she had put the
twelfth traveller into Room No. 11. She then went back to where she had
left the two travellers together, and asking the thirteenth traveller to
follow her, led him to No. 12, the remaining room. Thus all were
accommodated. Ask your friends to explain the mystery.