Amar, Samar and Umesh together can complete a book in 15 days. Amar and Samar together can complete the same book in 30 days. Umesh alone can complete the same book in how many days?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 30 days.
Amar, Samar, and Umesh together can complete the book in 15 days:
This means their combined rate of work = 1/15 books per day
⇒ A + S + U = 1/15 ..............(1)
Amar and Samar together can complete the book in 30 days:
This means their combined rate of work = 1/30 books per day
⇒ A + S = 1/30 ..............(2)
subtract equation (2) from equation (1):
⇒ (A + S + U) − (A + S) = 1/15 − 1/30
⇒ U = 1/15 − 1/30
⇒ U = 2/30 − 1/30 = 1/30 books per day
Days = 1/1/30 = 30days