Question

A jeweler has 5 rings, each weighing 18 g, made of an alloy of 10% silver and 90% gold. she decides to melt down the rings and add enough silver to reduce the gold content to 75%. how much silver should she add?

Answer 1

Silver = 10%
Gold = 90%

Amount of gold to be deducted
90/100 × 18 = 16.2 g

75/100 × 18 = 13.5

16.2 - 13.5 = 2.7

Amount o silver to added.
  2.7 × 5 = 13.5


Answer = 13.5 g