Question

A can complete a certain work in 35 days and B can complete the same work in 15 days. They worked together for 7 days, then B left the work. In how many days will A alone complete 60% of the remaining work?

• A. 15
• B. 18
• C. 10
• D. 7

Answer 1

Answer:

D. 7

Solution: GIven: A completes the work in 35 days B completes the work in 15 days Concept used: A's one day work is 1/35 B's one day work is 1/15 Calculation: A + B = (1/35) + (1/15) ⇒ A + B = (7 + 3)/105 = 2/21 Work completed by A + B in 7 days ⇒ (2/21) × 7 = 2/3 Remaining work = 1 - (2/3) = 1/3 1/3 work is left A will complete it in = 35 × (1/3) = 35/3 Asked in question 60% of the remaining work ⇒ (35/3) × (60/100) =7 ∴ A will take 7 days. By LCM method Time Total work(LCM of time) Efficiency(total work/time) A 35 3 105 B 15 7 A + B = 3 + 7 =10 A + B workes for 7 days = 10 × 7 = 70 Reamning work = 105 - 70 = 35 60% of the remaining work = 35 × (60/100) = 21 A complete it = 21/3 = 7 ∴ A will take 7 days.