P, Q and R can complete a work in 12, 9 and 15 days respectively. Working together, they will complete the same work in:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \(3\frac{39}{47}\) days
A person who finishes a job in \(n\) days does \(\frac{1}{n}\) of it in one day, and when people work together their one-day work is added. Taking the whole job as 180 units, the LCM of 12, 9 and 15, keeps the numbers whole.
P: \(180\div12=15\) units a day
Q: \(180\div9=20\) units a day
R: \(180\div15=12\) units a day
Together: \(15+20+12=47\) units a day
Days \(\displaystyle =\frac{180}{47}=3\frac{39}{47}\)