Multiple choice

A is twice as efficient as B. A can complete his work 30 days before B. If they work together, then in how much time can they complete the work?

  1. 10 days

  2. 20 days

  3. 60 days

  4. 80 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A is twice as efficient as B, so A takes half the time of B. Let B take 2x days and A take x days. 2x - x = 30, so x = 30. A takes 30 days, B takes 60 days. Together: (30 * 60) / (30 + 60) = 1800 / 90 = 20 days.

AI explanation

Since A is twice as efficient as B, the ratio of their efficiencies is 2 to 1, meaning the ratio of the time they take is 1 to 2. Let the time taken by A be x days, so B takes 2x days. The difference is 2x minus x = 30 days, so x = 30; thus, A takes 30 days and B takes 60 days. Their combined one day work is 1/30 + 1/60 = 3/60, which simplifies to 1/20, meaning they complete the work together in 20 days.

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