Multiple choice

A, B and C together can build a wall in 18 days. C is three times as productive as B and A alone can build the wall in 54 days. In how many days A and B working together can build the wall?

  1. 53 days

  2. 46 days

  3. 42 days

  4. 36 days
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let total work = 1 unit. A+B+C combined rate = 1/18. A's rate = 1/54. So B+C = 1/18-1/54 = 3/54-1/54 = 2/54 = 1/27. Given C is 3 times as productive as B, so C = 3B. Then B+3B = 4B = 1/27, so B = 1/108. A+B together = 1/54+1/108 = 2/108+1/108 = 3/108 = 1/36. Therefore, A and B together can build the wall in 36 days.

Keep practicing — related questions