| M 1 | M 2 | M 3 | Resulting Mix | |
| Copper | \(25 \%\) | \(100 \%\) | \(0 \%\) | \(30 \%\) |
| Iron | \(40 \%\) | \(0 \%\) | \(100 \%\) | \(50 \%\) |
| Weight in lbs | \(100 \) | \(x \) | \(y \) | \(100+x+y \) |
\(0.25(100)+x=0.3(100+x+y)\)
\(25 +x = 30 +0.3x +0.3y\)
\(0.7x = 5 +0.3y\)
\(x = \frac{50}{7} +\frac{3y}{7}\)
\(0.4(100)+y=0.5(100+x+y)\)
\(40 +y= 50 +0.5x +0.5y\)
\(-10+0.5y = 0.5x\)
\(-20 + y = x\)
\(-20+y = \frac{50}{7} +\frac{3y}{7}\)
\(y =47.5 \text{lbs} \)
\(x = 47.5-20 = 27.5 \text{lbs}\)
Answer: the weight of the copper is 27.5 lbs and the iron is 47.5 lbs