Material science-Specification of composition

[mugzieee]

Im given this problem:
Ge forms a substitutional solid solution with Si. find the weight% of Ge, that must be added to Si to yield an alloy that contains 2.43x10^21 Ge atoms per cubic centimetr. The densities of pure Ge and Si are 5.32 and 2.33 g/cm^3, respectively.

then I have a formula that says C1=(m1/m1+m2)*100% where C1 is the concentration in weight % of material 1 and m1 is the mass of material 1, and m2 is the mass of material 2. I use this formula, and i get 72% for Ge, but the correct answer is 11.7%. does anyone know what i am doing wrong?

 

[teknodude]

Is this problem from Materials Science and Engineering Intro by William D CallisteR?

If it is then it's question # 4.22. Anyway try doing #4.20 first, or just simply use the equation that's given in # 4.20.

 

[mugzieee]

it is that book, but it is in chapter 5, not chapter 4.