XAT 2012 — QA & DI Question 17
Answer the following question based on the information given below.
Ramya, based in Shanpur, took her car for a 400 km trip to Rampur. She maintained a log of the odometer readings and the amount of petrol she purchased at different petrol pumps at different prices (given below). Her car already had 10 litres of petrol at the start of the journey, and she first purchased petrol at the start of the journey, as given in table below, and she had 5 litres remaining at the end of the journey.
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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?
Answer & solution
- A
5
9
- C
10
- D
12
- E
15
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).