Ram prepares solutions of alcohol in water according to customers’ needs. This morning Ram has prepared 27 litres of a 12% alcohol solution and kept it ready in a 27 litre delivery container to be shipped to the customer. Just before delivery, he finds out that the customer had asked for 27 litres of 21% alcohol solution. To prepare what the customer wants, Ram replaces a portion of 12% solution by 39% solution. How many litres of 12% solution are replaced?
Explanation:
Let Ram replace x litres of 12% solution with 39% solution.
Hence, amount of alcohol in new solution = (27 – x) × 0.12 + x × 0.39 = 27 × 0.12 + x × 0.27
Now, new concentration of the solution is 21%, hence, volume of alcohol = 27 × .21
Hence, 27 × 0.12 + x × 0.27 = 27 × 0.21
Hence, 0.12 + x/100 = 0.21
Hence, x = 9.
Hence, option (b).
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