Tim:

First, convince yourself that it takes exactly 5 bridge traversals to move 4 people from one side to another.

Second, there is only one way to represent 17 as the sum of 5 integers drawn from among 1,2,5,10: 17=10+2+2+2+1.

Solution 1:

1,2,5,10        -          
5,10            ->             1,2             (2)
2,5,10          <-             1               (2)
2               ->             1,5,10         (10)
1,2             <-             5,10            (1)
                ->             1,2,5,10        (2)

Solution 2

1,2,5,10        -          
5,10            ->             1,2              (2)
1,5,10          <-             2                (1)
1               ->             2,5,10          (10)
1,2             <-             5,10             (2)
                ->             1,2,5,10         (2)

Are the notations clear?

Regards,
Alexander Bogomolny

Copyright © 1996-2008 Alexander Bogomolny

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