Multiple choice

There are three barrels, B1, B2 and B3, filled respectively with 60%, 75% and 80% mixtures of petrol in kerosene. The mixtures in the three barrels are taken in a certain ratio and mixed thoroughly to form a 7 10 mixture of petrol in kerosene. In this mixture, if the quantity of the solution taken from B3 is 2 5 less than the quantity taken from B1, by what percent is the quantity taken from B2 less or more than the quantity taken from B1?

  1. 20% less

  2. 10% less

  3. 10% more

  4. 20% more

  5. d
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the quantities from B1, B2, and B3 be x, y, and 3x/5 respectively. Equating the final petrol concentration to 70% gives 0.6x + 0.75y + 0.8(3x/5) = 0.7(x + y + 3x/5). Solving gives y = 0.8x, so B2 contributes 20% less than B1.

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