134 Geometrical Problemsplace the 1 on the top of the 3, or the 3 on the top of the 7, or the 2 on the 6,
or the 2 on the 4, but you must not place the I on the 2, or the 4 on the 7, as
that would be an odd and even together.
What are the fewest possible moves?
- RAILWAY SHUNTING
How are the two trains in our illustration to pass one another, and proceed
with their engines in front? The small sidetrack is only large enough to hold
one engine or one car at a time, and no tricks, such as ropes and flying
switches, are allowed. Every reversal-that is, change of direction-of an
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engine is counted as a move in the solution. What is the smallest number of
moves necessary?
To work on the problem, make a sketch of the track, and on it place
a nickel and three pennies (heads up) for the engine and three cars on the left,
and a nickel and two pennies (tails up) for the engine and two cars on the
right.(j) @ @
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375. ADJUSTING THE COUNTERS
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Place twenty-five counters in a
square in the order shown. Then it is
a good puzzle to put them all into
regular order so that the first line
reads I 2 3 4 5, and the second 6 7 8 9
10, and so on to the end, by taking up
one counter in each hand and making
them change places. Thus you might
take up 7 and 1 and replace them as I
and 7. Then take up 24 and 2 and
make them also change places,