In an alloy, copper and zinc are in the ratio 5 : 2. If 1.25 kg of zinc is added to 17.5 kg of the alloy, what is the ratio of copper to zinc in the new alloy?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 2 : 1
Only zinc is added, so the copper stays the same.
Copper \(\displaystyle =17.5\times\frac{5}{7}=12.5\) kg, zinc \(\displaystyle =17.5\times\frac{2}{7}=5\) kg
Zinc after adding \(=5+1.25=6.25\) kg
Copper : zinc \(=12.5:6.25=2:1\)
The new ratio is 2 : 1.