Multiple choice

Directions : Select the correct alternative from the given choices. lf A is 25% as efficient as B and can complete a certain work taking 15 days more than the time taken by B, in how many days will both A and B together complete the work?

  1. 4 days

  2. 5 days

  3. 7 days

  4. 10 days
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If A is 25% as efficient as B, then B is 4 times as efficient as A. If A takes x days, B takes x/4 days. Given x = (x/4) + 15, we find 3x/4 = 15, so x = 20. A takes 20 days and B takes 5 days. Together, they take (20 * 5) / (20 + 5) = 100 / 25 = 4 days.

AI explanation

Given A is 25% as efficient as B, the ratio of their efficiencies is 1:4. By the inverse efficiency formula, the ratio of their time taken is 4:1, meaning the 15 extra days A takes equals 3 parts of the ratio. Therefore, B takes 5 days and A takes 20 days for the whole job. Their combined one day's work is 1/20 plus 1/5, which equals 1/4, meaning together they complete the work in 4 days.

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