Average density of a copper-coated iron BB is 8.00g/mL. If the density for copper is 8.92 g/mL, and the density for iron is 7.43g/mL, what is the percentages of copper and iron in a BB?

Answer 1

Notice that mass is density*volume.

total mass=massiron*densityiron*volume + masscopper*densitycopper*volume

Now, divide by total mass

1= fractioniron*densityiron*volume/mass + fractionCu*densityCu*volume/mass.

now note that volume/mass=1/avgdensity

and that fractionCu=1-fractioniron

That should be enough for you to grunt through the algebra.

Answer 2

I am confused on what the fraction is?? and what is my volume? could you please clear this up?