Question

When they work alone, B needs 25% more time to finish a job than A does. They two finish the job in 13 days in the following manner: A works alone till half the job is done, then A and B work together for four days, and finally B works alone to complete the remaining 5% of the job. In how many days can B alone finish the entire job?

• A. 20
• B. 16
• C. 22
• D. 18

Answer 1

The Correct Option is A

The correct answer is (A):
Let the time taken by A to finish the job be “a” days.
Time taken by B to finish the job = 5/4 a days.
Part of the job completed when A and B worked together for 4 days = 1 = 1/2-5/100 = 9/20
4(1/a+1/5a/4) = 9/20 ⇒ a = 16
Time taken by B alone to complete the entire job = 5a/4 = 20 days.