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SSC CHSL 2025 PYQ — Question 67

SSC CHSL - 12 Nov 2025 - Shift 3 • Quantitative Aptitude • Q67

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A 40 kg alloy of German Silver contains Copper and Zinc in some proportion. It has 10% Zinc. How much pure Zinc (in kg) should be added to the alloy so that the new mixture contains 20% Zinc?

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Correct answer: B

Explanation

Alloy = 40 kg
Zinc content = 10%
New zinc content = 20%
Initial zinc = 10% of 40 kg = 4 kg
Let's assume x kg of pure zinc is added.
New amount of zinc = 4 + x
New total mixture = 40 + x
4+x40+x=201004+x40+x=155(4+x)=40+x20+5x=40+x4x=20x=5\frac{4 + x}{40 + x} = \frac{20}{100} \\ \frac{4 + x}{40 + x} = \frac{1}{5} \\ 5(4 + x) = 40 + x \\ 20 + 5x = 40 + x \\ 4x = 20 \\ x = 5
Pure zinc added = 5 kg