A can complete certain work in 40 hours and B can complete the same work in 60…
2018
A can complete certain work in 40 hours and B can complete the same work in 60 hours. In how many hours will the work be completed if A leaves 10 hours before the actual completion of the work?
- A.
39
- B.
42
- C.
44
- D.
30
Attempted by 18 students.
Show answer & explanation
Correct answer: D
Let the total time taken to complete the work be T hours.
A's work rate is 1/40 per hour and B's work rate is 1/60 per hour.
A works for (T - 10) hours, and B works for T hours.
The equation for total work is: (T - 10)/40 + T/60 = 1.
Multiply the entire equation by 120 (LCM of 40 and 60): 3(T - 10) + 2T = 120.
Simplify: 3T - 30 + 2T = 120 => 5T = 150 => T = 30 hours.
Final Answer: Option 4 (30)