Copper Stoichometry Ratio Problem
No serious mining operation would just dump a third of their desired product. 
 The question does say that the reactions are "part of the manufacture of copper." This does not preclude other reactions. With the given reactions alone we are not able to handle the surplus of $\ce{Cu2S}$.
$$\ce{\color{\red}{4CuFeS2} + 9 1/2 O2 + 4 SiO2 \rightarrow \color{\red}{Cu2S + Cu2O} + 2SO2 + 4FeSiO3}  \tag{1}$$
$$\ce{\color{\red}{2} Cu2S + 2 Cu2O \rightarrow 6Cu + SO2 +\color{\red}{Cu2S}}\tag{2}$$
However we can infer from the first reaction that the sulfide can react with oxygen to form the needed oxide to balance reduction and oxidation.
$$\ce{ Cu2S + 1 1/2O2 -&gt;  Cu2O + SO2}\tag{3}$$
The second equation can now become:
$$\ce{\color{\red}{2} Cu2S + 2 Cu2O +\color{\red}{1 1/2 O2} \rightarrow 8 Cu + 2 SO2 \tag{4}}$$
Thus in the first step $\ce{Cu2O \text{and} Cu2S}$ are produced according to quation 1.  In the second step they are reduced with aditional oxygen according to equation 4. To pove they balance first double equation 1.
$$\ce{8CuFeS2 + 19 O2 + 8 SiO2 \rightarrow \color{\red}{2Cu2S + 2Cu2O} + 4 SO2 + 8 FeSiO3}  \tag{5.1}$$
Add $\ce{1 1/2 O2}$ to each side
$$\ce{8CuFeS2 + \color{\red}{20 1/2 O2} + 8 SiO2 \rightarrow \color{\red}{2Cu2S + 2Cu2O + 1 1/2 O2 }+ 4 SO2  + 8 FeSiO3}  \tag{5.2}$$
Substitute the red products with equation 4 reactants.
$$\ce{8CuFeS2 + \color{\red}{20 1/2 O2} + 8 SiO2 \rightarrow \color{\red}{8 Cu + 2 SO2}+ 4 SO2  + 8 FeSiO3}  \tag{5.3}$$
This Gives a final balanced equation of 
$$\ce{8CuFeS2 + 20 1/2 O2 + 8 SiO2 \rightarrow 8 Cu + 6 SO2  + 8 FeSiO3}  \tag{5.4}$$
As you can see on a molar eatio $\ce{CuFeS2\text{:}Cu}$ is 1:1 after accounting for the additional oxygen needed.