MODELING REAL LIFE Brass is an alloy composed of \( 55 \% \) copper and \( 45 \% \) zinc by weight. You have 25 ounces of copper. How many ounces of zinc do you need to make brass? Round your answer to the nearest tenth. about \( \square \) ounces of zinc

To make brass, you need to maintain the ratio of copper to zinc in the alloy. Since brass is composed of \( 55\% \) copper and \( 45\% \) zinc, we can set up a proportion based on the \( 25 \) ounces of copper you have. If \( x \) is the amount of zinc needed, the relationship can be expressed as: \[ \frac{25}{x} = \frac{55}{45} \] Cross-multiplying gives: \[ 25 \times 45 = 55 \times x \] \[ 1125 = 55x \quad \Rightarrow \quad x = \frac{1125}{55} \approx 20.5 \] So, you need about \( 20.5 \) ounces of zinc to make your brass! To make this process easier for future calculations, remember that proportional relationships can be your ally. Always set them up carefully and isolate the variable you're trying to find! One common mistake is forgetting to maintain the percentage relationships when combining materials—double-check your proportions to avoid mix-ups!