Sections A – Data Interpretation and Quantitative Ability

6. A manufacturer has 200 litres of acid solution which has 15% acid content. How many litres of acid solution with 30% acid content may be added so that acid content in the resulting mixture will be more than 20% but less than 25%?

A. More than 100 litres but less than 300 litres

B. More than 120 litres but less than 400 litres

C. More than 120 litres but less than 300 litres

D. None of the above

Solution:

Let the volume of the solution with 30% acid content lie between v₁ and v₂, where for v₁ we get a 20% acid solution and for v₂ we get a 25% acid solution as the resultant mixture.

15% (200) + 30% (v₁) = 20% (200 + v₁)

Þ30 + 0.3v₁ = 40 + 0.2v₁

Þv₁ = 100 litres and

15% (200) + 30% (v₂) = 25% (200 + v₂)

Þ30 + 0.3v₂ = 50 + 0.25v₂

Þv₂ = 400 litres.

Therefore, for the acid content in the resultant mixture to lie between 20% and 25%, the volume of the 30% concentration acid solution must lie between 100 litres and 400 litres. Choice (C)