What is the percentage of zinc in X ?
For the next two (02) items that follow : X is an alloy of copper and zinc. Y is an alloy containing 80% of copper, 4% of zinc and 16% of tin. A fused mass of X and Y is found to contain 74% of copper, 16% of zinc and 10% of tin.
- A. 40%
- B. 36% ✓
- C. 34%
- D. 30%
Correct Answer: B. 36%
Explanation
Since X only contains copper and zinc, and copper was determined to be 64%, the remaining percentage must be zinc. 100\% - 64\% = 36\%. Alternatively, using zinc balance: Z_x(3k) + 0.04(5k) = 0.16(8k) \implies 3Z_x + 0.20 = 1.28 \implies 3Z_x = 1.08 \implies Z_x = 0.36 = 36\%.
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