Multiple choice

A and B can complete a job together in 12 days. If A is twice as efficient as B, then in how many days can B alone complete the work?

  1. 18

  2. 9

  3. 36

  4. 12
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let B's efficiency be 1 unit/day, then A's is 2 units/day. Combined efficiency = 3 units/day. Total work = 12 * 3 = 36 units. B alone takes 36 / 1 = 36 days.

AI explanation

Using the efficiency ratio method, the ratio of the efficiencies of A and B is 2:1. Their combined efficiency becomes 3 units per day, meaning their total work is 12 days times 3 units, or 36 units. Since B has an efficiency of 1 unit per day, B alone needs 36 units divided by 1 unit per day, equaling 36 days to finish the work.

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