Isolating 6 gallons of water with 5 and a 7 gallon jugs of water

Factual Questions
1

How can you isolate 6 gallons of water from a desert oasis with only one 7 and one 5 gallon barrel?

2

  1. Fill up the 7 gallon barrel. Pour enough water from the 7 gallon barrel into the 5 gallon one to fill the 5 gallon barrel. 2 gallons of water will remain in the 7 gallon barrel.

  2. Empty out the 5 gallon barrel and pour the 2 gallons of water into the 5 gallon barrel. Fill up the 7 gallon barrel again and pour 3 gallons from the 7 gallon barrel into the 5 gallon barrel. 4 gallons of water will remain in the 7 gallon barrel.

  3. Empty out the 5 gallon barrel and pour the 4 gallons of water from the 7 gallon barrel to the 5 gallon barrel. Fill up the 7 gallon barrel. Pour 1 gallon from the 7 gallon barrel into the 5 gallon barrel. 6 gallons of water will remain in the 7 gallon barrel.

3

Simplest way I can think of:
Fill up the 5 gallon jug, empty into the 7.
Fill up the 5 gallon again and from it fill up the 7, leaving 3 gallons. Empty the 7 gallon and pour the 3 gallons into it.
Fill up the 5 gallon again and fill up the 7 gallon from it, leaving 1 gallon in the 5 gallon jug.
Empty the 7 gallon jug, pour the 1 gallon into it.
Add 5 more gallons.
Voila!

4

Beat me by 2 minutes.
Same theory in reverse.

5

A variation of this (involving 3 and 5 gallon jugs, with a target of 4 gallons) was in Die Hard with a Vengeance.

6

Fill up the 7th gallon thing half way in between the 5 and 7 tops:)