P alone can complete a work in 16 days and Q alone can complete the same work in 20 days. P and Q start the work together but Q leaves the work 7 days before the completion of work. In how many days the total work will be completed?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 12 days.
| Understanding/Application |
|
Let total work to be done = L.C.M.(16,20) = 80 units P's efficiency = 80/16 = 5 units/day Q's efficiency = 80/20 = 4 units/day Let the work is finished in days, then P alone worked for 7 days, and P and Q together worked for (t - 7) day. |
|
ATQ - 9(t - 7) + (5 × 7) = 80 9t - 63 + 35 = 80 9t = 108 t = 108/9 = 12 days |