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GATE 2018 EC – Question 7

General Aptitude · Quantitative Aptitude: Arithmetic and Number Computation · 2 marks · Multiple choice

Two alloys A and B contain gold and copper in the ratios of 2:3 and 3:7 by mass, respectively. Equal masses of alloys A and B are melted to make an alloy C. The ratio of gold to copper in alloy C is ________.

  1. 5:10
  2. 7:13
  3. 6:11
  4. 9:13

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Correct answer: (B) 7:13

Explanation

Take 10 kg of each alloy. A has $4$ kg gold and $6$ kg copper, and B has $3$ kg gold and $7$ kg copper. So C has $7$ kg gold and $13$ kg copper, a ratio of $7:13$.