# Homework Help: Mass range

1. Sep 8, 2008

### metalmagik

1. The problem statement, all variables and given/known data
Brass is an alloy of copper and zinc. Varying the mass percentages of the two metals produces brasses with different properties. A brass called yellow zinc has high ductility and strength and is 34%-37% zinc by mass.
(a) Find the mass range (in g) of copper in 185 g of yellow zinc.
(b) What is the mass range (in g) of zinc in a sample of yellow zinc that contains 46.5 g of copper?

2. Relevant equations
No specific formulas

3. The attempt at a solution
I got part (a), This is what I did roughly
(185 g)(.34) = 62.9 g of zinc 185 g - 62.9 g = 122.1 g of copper
(185 g)(.37) = 68.45 g of zinc 185 g - 68.45 g = 116.55 g of copper

Mass range = 116.55 g - 122.1 g of copper

I think that's correct. Now I just have no idea how to do part (b), there is no mass range for copper, just one number, 46.5.

Any ideas? Thanks guys :)

2. Sep 9, 2008

### Staff: Mentor

If total is 100% and Zn is 34%-37%, how much is Cu?

3. Sep 9, 2008

### metalmagik

Ah I see, I think I got it now. I work backwards using an average percentage and actual mass value to get the total mass of the yellow zinc. Thank you!