Question
A 120 litres solution of alcohol and water contains 30%
alcohol. When Q litres of alcohol and (Q - 4) litres of water are added to the solution, the quantity of alcohol becomes 3/7 of the total solution. What is the value of (Q - 13)?Solution
ATQ,
Quantity of alcohol in the initial solution = 0.30 × 120 = 36 litres Quantity of water in the initial solution = 120 - 36 = 84 litres ATQ: 36 + Q = (3/7) × (120 + Q + Q - 4) → 36 + Q = (3/7) × (120 + 2Q - 4) → 36 + Q = (3/7) × (116 + 2Q) → 7(36 + Q) = 3(116 + 2Q) → 252 + 7Q = 348 + 6Q → Q = 96 Required value = Q - 13 = 96 - 13 = 83
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