Multiple choice

A measuring cylinder is filled one third full with ethanol. A mixture of ethanol, water and propanol is used to fill the measuring flask to capacity. What fraction of the final mixture is ethanol?

  1. $\dfrac 19$
  2. $\dfrac 39$
  3. $\dfrac 59$
  4. $\dfrac 79$
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C Correct answer
AI explanation

Assume the measuring cylinder has a total capacity of 9 units. Since it is already one third full of ethanol, it contains 3 units of pure ethanol. This leaves 6 units of empty space, which is filled with a mixture containing ethanol, water, and propanol in equal fractions. The added mixture therefore brings in 2 more units of ethanol, making the total amount of ethanol 3 + 2 = 5 units. The final fraction of ethanol in the mixture is 5 out of 9.

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