Multiple choice

P and Q are two alloys of gold and copper prepared by mixing metals in the ratio 7: 2 and 7: 11 respectively. If equal quantities of the alloys are melted to form a third alloy R, Find the ratio of gold and copper in the third alloy?

  1. $6: 7$
  2. $7: 5$
  3. $4 : 3$
  4. $5: 6$
  5. $3: 2$
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B Correct answer
Explanation

Alloy P: Gold:Copper = 7:2, so Gold = 7/9, Copper = 2/9. Alloy Q: Gold:Copper = 7:11, so Gold = 7/18, Copper = 11/18. Equal quantities mixed: Total Gold = 7/9 + 7/18 = 14/18 + 7/18 = 21/18 = 7/6. Total Copper = 2/9 + 11/18 = 4/18 + 11/18 = 15/18 = 5/6. Ratio Gold:Copper = 7:5.

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