A and B can complete a job together in 12.5 days; B and C can complete the same job together in 18.75 days, while C and A can complete the same job together in 15 days. In how many days will A, B, and C together be able to complete the same job alongside D, who is only 40% as efficient as C?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. .
Calculations:
Total work (LCM 12.5, 18.75, 15) = 75 units
Amount of work done by A and B in 1 day = 75/12.5 = 6 units
Amount of work done by B and C in 1 day = 75/18.75 = 4 units
Amount of work done by A and C in 1 day = 75/15 = 5 units
Hence, work done by all three in a day = 6 + 4 + 5 = 15/2 = 7.5 units
Hence, work done by C = 7.5 - 6 = 1.5 units
Hence the work done by D = 0.4 × 1.5 = 0.6 units
The total work done by all 4 in a day = 7.5 + 0.6 = 8.1 units
Hence, time taken by A, B, C, and D together = 75/8.1 = days