A, B and C can complete a certain work in 12, 15 and 20 days respectively, A and B together start the work and B leaves after working 4 days. A and C together, will complete the remaining work in______days.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 3.
Let the total work to be done (LCM of 12, 15 and 20) be 60 units.
Efficiency of A = 60/12 = 5 units/day
Efficiency of B = 60/15 = 4 units/day
Efficiency of C = 60/20 = 3 units/day
Work done by (A + B) in 4 days = 4 × (5 + 4)
⇒ 4 × 9 = 36 units
Remaining work = 60 - 36 = 24 units
Time taken byb (A + C) to complete remaining work = 24/(5 + 3)
⇒ 24/8 = 3 days