This is something that came up with me. I often buy a 4L jug of milk. I noticed that sometimes the milk goes bad before I finish it and I end up pouring some of it out.
So I thought I might buy 2L milk instead. Then I saw the prices:
4L milk: $5.69
2L milk: $3.99
which leads to the practical math problems.
1) how much (in litres) of a 4L jug can you pour out and still be better off than buying 2L
2) the main body of a 4L jug is around 8 inches high. assuming the entire 4L content fits in that 8 inches, how many inches can you pour out off the bottom of a 4L and still be ahead
we can assume that the buyer will always be able to finish a 2L milk. so as a baseline the 2L is always fully consumed with no losses
these should be solvable by a high school student or a better junior high. I'll let it sit for a couple of days then post the answer in the comments.