Two persons A and B can complete a task in 10 days and 15 days, respectively. They work together and A leaves 5 days before the task is completed. After that. B alone completes the remaining task. The number of days taken to complete the whole task is:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 9.
Let total time = x days
A worked for (x − 5) days, B worked for x days.
A's 1 day work = 1/10, B's = 1/15
Work done = (x − 5)(1/10) + x(1/15) = 1
LCM = 30:
⇒ (x−5)(3) + x(2) = 30
⇒ 3x − 15 + 2x = 30 ⇒ 5x = 45 ⇒ x = 9