George Polya "the great problem solver"?

Question

How can you bring up from the river exactly 6 quarts of water when you have only two containers, a 9 quart pail and a 4 quart pail, to measure with?

Also, to be done in exactly 8 steps.

Answer 1

1. Fill the 9 quart container.
2. Measure out 4 quarts and dump.
3. Measure out 4 MORE quarts and dump.
4. Pour the last quart into the 4 quart container.
5. Fill the 9 quart container.
6. Pour from the 9 quart container to fill the 4 quart container (three quarts).
7. Dump the 4 quart container.
8. You have exactly 6 quarts left in the 9 quart container. YAY

Answer 2

Fill up the 9 quart pail.
Using the 9 quart pail fill the 4 quart pail leaving 5 quarts in the 9 quart pail.

Dump out the 4 quarts and refill from the 9 quart pail leaving only 1 quart in the 9 quart pail.

Dump out the 4 quart pail and fill it with the 1 quart remaining in the 9 quart pail.

Fill up the 9 quart pail, now fill the rest of the 4 quart pail (still has 1 quart in it) using 3 quarts from the 9 quart pail leaving exactly 6 quarts in the 9 quart pail.