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In 50 gm alloy of gold and silver the gold is 80 % by weight. How much gold should be mixed with this alloy so that the weight of gold would become 95 %?

Correct answer: B. 150 gm

  • A. 200 gm
  • B. 150 gm
  • C. 50 gm
  • D. 10 gm

Explanation

Initially, gold weighs 80% of 50 g, so gold = 0.8 × 50 g = 40 g and silver = 10 g. If x g of gold is added, (40 g + x)/(50 g + x) = 0.95; solving gives 40 + x = 47.5 + 0.95x, so x = 150 g. Students may choose 50 g by ignoring that the added gold also increases the total alloy weight.

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