Question

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%?

Accepted Answer

C. Let $x$ litres of 30% solution be added. Case 1: Acid content > 20%: $$15\%(200) + 30\%(x) > 20\%(200 + x)$$ $$30 + 0.3x > 40 + 0.2x \implies 0.1x > 10 \implies x > 100$$ Case 2: Acid content < 25%: $$15\%(200) + 30\%(x) < 25\%(200 + x)$$ $$30 + 0.3x < 50 + 0.25x \implies 0.05x < 20 \implies x < 400$$ Thus, $100 < x < 400$ litres.

Mixtures and Alligations Acid Solution

Explanation

Practise this under exam conditions