"A craftsperson wishes to make an alloy from an alloy which is 40% gold and another which is 60% gold. How many ounces of the 40% alloy need to be used to get 5 ounces that are 55% gold?"
I was leaning towards C, because... Well, lemme see if I can explain it. 55% is closer to 60 than it is 40, so it would only be logical that there would be more of the 60% alloy than the 40% alloy. The main reason I'm confused is because one of my quite smart friends told me it was D, so I have no idea.