Ask the company to arrange the whole set of dominoes whilst you are
absent in any way they please, subject, however, to domino rules--a
6 placed next to a 6, a 5 to a 5, and so on. You now return and
state that you can tell, without seeing them, what the numbers are
at either end of the chain. The secret lies in the fact that the
complete set of 28 dominoes, arranged as above-mentioned, forms a
circle or endless chain. If arranged in a line the two end numbers
will be found to be the same, and may be brought together, completing
the circle. You privately abstract one domino (not a double), thus
causing a break in the chain. The numbers left at the ends of the
line will then be the same as those of the “missing link” (say the
3-5 or 6-2.) The trick may be repeated, but you must not forget to
exchange the stolen domino for another.
237. A busman not having room in his stables for eight of his horses
increased his stable by one half, and then had room for eight more
than his whole number. How many horses had he?