Question

An alloy of copper and zinc contains 80% zinc by weight. If in 350 g of this alloy 50 g of copper is added, then what is percentage of copper in the new alloy
1. 30%
2. 40%
3. 32%
4. 25%

Answer 1

Correct Answer - Option 1 : 30%

Given:

An alloy of copper and zinc contains 80% zine by weight

Total alloy = 350g

Calculation:

According to the question,

Zinc by weight = 350 × 80/100 = 280g

Copper by weight = 350 - 280 = 70g

This alloy 50g of copper is added = 70 + 50 = 120g

New alloy = 280 + 120 = 400g

Required % = 120/400 × 100 = 30%

∴ Percentage of copper in the new alloy is 30%.