An alloy of brass is composed of 84.6% copper, 5.20% tin, 6.70% lead, and zinc. The number of pounds of zinc required to make 520.0 pounds of alloy is "_____"

Question

Obviously this is a homework question for my trade school. What I don't get about this is the wording. The zinc equals 3.5% of an alloy from what I put together. I don't understand though. Do these percentages amount to the percentages of a pound of the named material? The way it's worded doesn't seem to make sense to me. If I did this the way my brain is trying to put it together, the answer would be 148.5714285714286. Can somebody fact check this for me?

Answer 1

Hi Devon,

I would also interpret the given percentages as weight material. So yes, the given percentages are the percents of each metal in a pound of the alloy. You are also correct that the alloy in question is 3.5% Zinc by weight, which results with the conversion factor: (0.035 lb Zn/1 lb alloy)

So, for 520 lb of your alloy, you get: (520 lb alloy)*(0.035 lb Zn/1 lb alloy) = 18.2 lb of Zinc.