Correct Answer - Option 3 : 10 days
Given:
Time taken by A to complete 20% work = 4 days
Time taken by B to complete 33.33% of work = 10 days
They worked together for 9 days
C completed the remaining work in 6 days
Formula used:
Work = Time × Efficiency
Calculation:
Time taken by A to complete 100% work = 4 × 5 = 20 days
Time taken by B to complete 100% work = 10 × 3 = 30 days
L.C.M of 20 and 30 = 60 = Total work
Efficiency of A = 60/20 = 3 units/day
Efficiency of B = 60/30 = 2 units/day
Worked done by A and B together in 9 days = (3 + 2) × 9
⇒ 45 units
Remaining work = (60 – 45) units
⇒ 15 units
C can complete the remaining work in 6 days
Efficiency of C = 15/6 = 2.5 units/day
Total efficiency of B and C = (2 + 2.5) units/day
⇒ 4.5 units/day
Now, 75% of total work = 75% of 60 units
⇒ 45 units
Required time = 45/4.5 days
⇒ 10 days
∴ B and C can complete 75% work in 10 days
