Exams › SSC CGL (Prelims) › General

Acids X, Y, and Z have concentrations of 20%, 30%, and 40% respectively. They are mixed in the ratio 3 : 5 : a to obtain a mixture of 30% concentration. Find the value of 'a'.

1. 4
2. 1
3. 3
4. 2

Correct answer: 3

Solution

Setting up the weighted average: (0.20x3 + 0.30x5 + 0.40xa) / (3+5+a) = 0.30. This simplifies to 0.6 + 1.5 + 0.4a = 0.9 + 1.5 + 0.3a, giving 0.1a = 0.3, so a = 3.

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