Question

A can finish 80% of a task in 12 days and B can finish 20% of the same task in 2 days. They started the task together, but B left after 2 days and A continued to work. In how many days was the entire task completed?

• A. 17.5
• B. 10
• C. 15
• D. 12

Answer 1

Answer:

D. 12

Given: A can finish 80% of task = 12 days B can finish 20% of the same task = 2day Calculations: A's 80% of work = 80/100 of work ⇒ 4/5 th of work 4/5 th of work completed = 12days Total work completed =12 × 5/4 ⇒ 15 days B's 20% of work = 20/100 of work ⇒ 1/5 th of work 1/5 th of work completed = 2days Total work completed = 2 × 5 ⇒ 10 days A and B started the work together and worked for 2 days = 2/15 + 2/10 ⇒ (2 × 2 + 2 × 3)/30 = 10/30 ⇒ 1/3 of completed in 2 days Remaining work = 1 - 1/3 ⇒ 2/3 of work 2/3 of work done by A = (2/3) × 15 ⇒ 10 days From starting to ending total days to complete the work = 10 + 2 ⇒ 12 days ∴ The total number of days taken to complete a task is 12 days