Oil and vinegar

A cunning speculator begins in business with a batch of barrels of oil and vinegar. We do not know how many barrels there are each one but we know that its first client paid $ 14 for each barrel, which paid double for the gallon of oil than for the vinegar and that left a single barrel.

What barrel leaves?

The client bought the oil barrels of 13 and 15 gallons at 50 cents per gallon, and the vinegar barrels of 31, 18 and 8 gallons to twenty -five cents per gallon. This Leave 19 gallons , that can contain both oil and vinegar.