An alloy contains 40% of silver, 30% of copper and 30% of nickel. How much silver (in kg) should be added to 25kg of the alloy so that the new alloy contains 50% of silver?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 5
An alloy contains 40% of silver, 30% of copper, and 30% of nickel.
Total weight of the alloy = 25 kg
The required percentage of silver = 50%
The ratio of silver, copper and nickel = 40 : 30 : 30 = 4 : 3 : 3
Let the total silver, copper, and nickel be 4x, 3x, and 3x respectively.
4x + 3x + 3x = 25
10x = 25
4x = (25/10) × 4 = 10
The weight of silver in 25 kg = 10 kg
Let the amount of silver added be y kg.
(10 + y) = 1/2 × (25 + y) [50% = 1/2]
20 + 2y = 25 + y
2y - y = 25 - 20
y = 5