So this is something that happened to me a few days ago, and it makes for a nice puzzle.
My wife asked me to pour soy sauce and vinegar into two saucers, equal parts (1:1 ratio).
I poured the vinegar into each saucer. But then I poured twice as much soy sauce as was needed into the first saucer.
Question: How do you fix this easily?
My wife solved it without thinking.