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Puzzle ZBOE 



??

Using a tap, a seven gallon container and a eleven gallon container, can you measure exactly 9 gallons?

You may empty the containers down the drain.

Puzzle Copyright © Kevin Stone

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Answer
Here are the contents of the containers after each stage:
A  B
0  11  fill B
7  4   fill A from B
0  4   empty A
4  0   fill A from B
4  11  fill B
7  8   fill A from B
0  8   empty A
7  1   fill A from B
0  1   empty A
1  0   fill A from B
1  11  fill B
7  5   fill A from B
0  5   empty A
5  0   fill A from B
5  11  fill B
7  9   fill A from B
0  9   empty A

This leaves 9 gallons in container B.

 

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