Interview Question for Senior Software Engineer at Blue Coat Systems:

This is an old puzzle; it's often seen with different bucket sizes, but the idea is the same. I think they even did a version of it in one of the Die Hard movies.

Fill the medium bucket with 5 lt. Pour 3 from medium to small, leaving 2 in medium.
Pour small into large, medium into small.
Now you have 2 in small, empty medium, 13 in large.
5 into medium from large
1 into small from medium, filing small, and leaving 4 in medium
Empty small into large.
Problem solved - empty small, 4 in medium, 11 in large.