Mathematical_Recreations-Kraitchik-2e

Permutational Problems
get onto the siding. Train A passes the siding and allows
train B to pull out of the way. Train A comes back and
leaves some cars of train B on the siding, backs past the
switch and pulls out of the way. Train B recaptures the cars
on the siding and pulls off the siding out of the way. These
operations are continued until train A has dropped all the
cars of train B that it had picked up. Train A then goes on
its way, train B picks up the last installment of cars, and
goes on its way.
If the locomotive of train A is not sufficiently strong, the
B A
B'
B'
A
B
FIGURE 104.
switching may be modified as follows: When train A is to the
right of the switch preparatory to picking up the first installment
of B's cars, it leaves all of its cars on the main track,
until it has finished switching B's cars. B behaves as before.
When the portion of train B containing the engine is on the
siding, the engine of train A first pushes B's cars out of the
way beyond the siding, then goes back and pulls its cars out
of the way before the part of B containing the engine pulls
off the siding. Then every time train A leaves an installment
of B's cars on the siding its engme must first leave its
own cars to the right of the switch, go back to pick up B's
cars to leave some on the siding, push the rest of B's cars that