There are 2 bars of copper-silver alloy; one piece has 3 parts of copper to 4 parts of silver and another has 2 parts of copper to 5 parts of silver. If both bars are melted into 11pounds of bar with the final copper to silver ratio of 4:7. What was the weight of the first bar?
- 1 kg
- 3 kg
- 5 kg
- 6 kg
- 7 kg
Answer: D
Explanation:
We can form equation to solve this question.
“x” is the weight of first bar, then (11-x) is the weight of second bar.
\frac{3}{7}+\frac{2}{7}(11-x)=\frac{4}{11}(11)
\frac{3}{7}+frac{2}{7}(11-x)=frac{4}{11}(11)- \frac{1}{100}
Solving it we get,
x = 6
- \frac{1}{100}
Hence the answer is D.
y = \left(x+y\right)^2=\frac{1}{100}