P, Q and R are working on a project. P can complete the work alone in 10 days, Q completes the work alone in 15 days and R completes the work alone in 18 days. But Q leaves the project 5 days before the completion of the project and R leaves after 3 days, when Q leaves. Find the total time required to complete a project.
P, Q and R are working on a project. P can complete the work alone in 10 days, Q completes the work alone in 15 days and R completes the work alone in 18 days. But Q leaves the project 5 days before the completion of the project and R leaves after 3 days, when Q leaves. Find the total time required to complete a project. Correct Answer 6.5 days
Given:
P can complete the work = 10 days
Q completes the work = 15 days
R completes the work = 18 days
Calculation:
Let work completes in x days.
Q works for (x – 5) days
P works for x days
R works for (x – 5 + 3) days
= (x – 2) days
According to question:
(x/10) + (x - 6)/15 + (x - 3)/18 = 1
⇒ {9x + 6(x - 5) + 5(x - 2)}/ 90 = 1
⇒ 9x + 6x – 30 + 5x – 10 = 90
⇒ 20 x – 40 = 90
⇒ 20x = 90 + 40
⇒ 20x = 130
⇒ x = 6.5 days
∴ Total time required to complete the project is 6.5 days.
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Feb 20, 2025