Multiple choice

A chemist buys two different types of aldehyde solutions for some experiment. In the first solution, the ratio of aldehyde to water is 3 : 4, and in the second solution, it is 5 : 6. If he mixes the two given aldehyde solutions and makes a third solution of 18 litres, in which the ratio of aldehyde to water is 4 : 5, then the quantity of the first solution (whose ratio is 3 : 4) required to make 18 litres of the third kind of solution is

  1. 6 l

  2. 7 l

  3. 8 l

  4. 9 l

  5. 10 l
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let x be the amount of the first solution. Aldehyde content: (3/7)x + (5/11)(18-x) = (4/9)*18 = 8. Solving for x: (3/7)x + 90/11 - (5/11)x = 8. (33-35)/77 x = 8 - 90/11 = -2/11. -2/77 x = -2/11. x = 7.

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