536 Puzzles and Curious Problems

(Elliott) #1
Answers 393

below the second player (B) puts off defeat as long as possible. In the second
game he prevents A scoring 17 or 30, but has to give him 24 and 37. In the
third game he prevents A scoring II or 24, but has to give him 17,30, and 37.
Notice the important play of the 3 and the 5.

A B A B A B

4 I (a) (^4) I 4 I
3 I (b) 3 I 3 4
(II) 2 I (11) 2 3 (d) (17) 5
(17) 5 I (c) 5 I 3 4
3 2 (24) 4 3 (e) (30) 5 (j) I
(24) I 2 5 I 3
(30) 4 (37) 4 (37) 2
3 2
(37) I
(a) Or A will score II next move. (b) B could not prevent A scoring II or
17 next move. (c) Again, to prevent A immediately scoring 24. (d) Prevent-
ing A scoring 17, but giving him 24. (e) Preventing A scoring 30, but giving
him the 37. (j) Thus A can always score 24 (as in the last game) or 30 (as
in this), either of which commands the winning 37.



  1. THE 22 GAME


Apart from the exhaustion of cards, the winning series is 7, 12, 17,22. If you
can score 17 and leave at least one 5-pair of both kinds (4-1, 3-2), you must
win. If you can score 12 and leave two 5-pairs of both kinds, you must win.
If you can score 7 and leave three 5-pairs of both kinds, you must win. Thus,
if the first player plays a 3 or 4, you playa 4 or 3, as the case may be, and score



  1. Nothing can now prevent the second player from scoring 12, 17, and 22. The
    lead of 2 can also always be defeated if you reply with a 3 or a 2. Thus, 2-3,
    2-3, 2-3, 2-3 (20), and, as there is no remaining 2, second player wins.
    Again, 2-3, 1-3, 3-2, 3-2 (19), and second player wins. Again, 2-3, 3-4 (12),
    or 2-3, 4-3 (12), also win for second player. The intricacies of the defence 2-2
    I leave to the reader. The best second play of first player is a I.
    The first player can always win if he plays I, and in no other way. Here are
    specimen games: 1-1,4-1,4-1,4 (16) wins. 1-3, 1-2,4-1,4-1,4 (21) wins.
    1-4,2 (7) wins. 1-2,4 (7) wins.

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