Multiple choice

In two alloys Copper and zinc in the ratio of 3:4 and 3:2 respectively. 28 kg of 1stalloy and 35 kg of 2nd alloy and some quantity of pure zinc is melted together. The final alloy has copper and zinc in the ratio of 4:5. Find the amount of pure zinc melted?

  1. 15.35

  2. 11.25

  3. 15

  4. 16

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Alloy 1: 28 kg (3:4) -> 12 kg Cu, 16 kg Zn. Alloy 2: 35 kg (3:2) -> 21 kg Cu, 14 kg Zn. Total Cu = 33 kg. Total Zn = 30 + x kg. Ratio 33/(30+x) = 4/5. 165 = 120 + 4x. 45 = 4x, x = 11.25.

AI explanation

In the first alloy, the copper quantity is 28 multiplied by 3 and divided by 7, which is 12 kg, and in the second alloy, the copper quantity is 35 multiplied by 3 and divided by 5, which is 21 kg. The final mixture has a copper to zinc ratio of 4 to 5, meaning the total copper of 33 kg corresponds to 4 parts, so each part equals 8.25 kg. The final mixture requires 5 parts of zinc, which totals 41.25 kg. By calculating the initial zinc amounts as 16 kg from the first alloy and 14 kg from the second alloy, the total initial zinc is 30 kg, meaning the added pure zinc is 41.25 minus 30, yielding 11.25 kg.

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