Multiple choice

A container contains a mixture of propene and methane in the ratio 5 : 1. Eighteen litres of mixture is taken out from the container and 6 litres of pure methane is added in the container. If the resultant ratio between propene and methane in the container is 3 : 1, what was the initial quantity (in litres) of the mixture in the container before replacement?

  1. 54

  2. 62

  3. 72

  4. 84

  5. 92
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let initial propene be 5x and methane be x. Total = 6x. Removing 18L removes 15L propene and 3L methane. Remaining: 5x - 15 propene, x - 3 methane. Adding 6L methane: 5x - 15 propene, x + 3 methane. Ratio (5x - 15) / (x + 3) = 3 / 1. 5x - 15 = 3x + 9, so 2x = 24, x = 12. Initial mixture = 6 * 12 = 72L.

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