Question

A alone can complete a work in 14 days and B alone can complete the same work in 21 days. A and B start the work together but A leaves the work after 4 days of the starting of work. In how many days B will complete the remaining work?

• A. 9 days
• B. 16 days
• C. 12 days
• D. 11 days

Answer 1

Answer:

D. 11 days

Solution: Given: A can complete the work in 14 days B can complete the work in 21 days Concept: In this type of question always imagine the total work as LCM of time taken by individuals to perform the work. Formula used: Efficiency = Total work/Time taken Calculation: Let the total work be LCM of 21, 14 i.e 42 unit So, Efficiency of A = 42/14 = 3 unit/day Efficiency of B = 42/21 = 2 unit/day Efficiency of (A + B) = 5 unit/day According to Question, A and B work for 4 days and performed work = 4 × 5 = 20 unit Remaining work left = 42 – 20 = 22 unit B completes the remaining work = 22/2 = 11 days ∴ Time taken by B to complete the remaining work is 11 day