Question

A and B can do a job in 10 days and 5 days, respectively. They worked together for two days, after which B was replaced by C and the work was finished in the next three days. How long will C alone take to finish 60% of the job?

• A. 18
• B. 30
• C. 25
• D. 24

Answer 1

Answer:

A. 18

Solution: Given: A can do a job in 10 days B can do a job in 5 days Formula used: Efficiency = Total work/Time taken Calculation: LCM of 10 and 5 = 10 = Total work Efficiency of A = 10/10 = 1 unit/day Efficiency of B = 10/5 = 2 units/day A and B work for 2 days ⇒ (1 + 2) × 2 units ⇒ 6 units Remaining work = (10 – 6) units ⇒ 4 units A and C can complete the remaining work in 3 days A and C one day work ⇒ 4/3 C one day work ⇒ (4/3) – 1 ⇒ 1/3 C can complete 60% of work in ⇒ 6 ÷ (1/3) ⇒ 18 days ∴ C can complete 60% of work in 18 days.