Solve this - How can You measure 1 Gallon of juice out of a Barrel?

Question:-

How can you measure 1 gallon of juice out of a barrel, if all you have available is a 3-gallon and a 5-gallon pitcher?
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Answer:-

Fill the 3 gallon pitcher and pour it into the 5 gallon pitcher. 

Now, fill the 3 gallon pitcher again and fill the 5 gallon pitcher to capacity. What remains in the 3 gallon pitcher is one gallon of juice.