Mother, daughter and son can do a work in 3, 4 and 5 days respectively. How many days will they take to complete the work, if they work together?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \(1\frac{13}{47}\) days
A person who finishes a work in \(n\) days does \(\frac{1}{n}\) of it in one day. Working together, the one-day works add up, and the time taken is 1 divided by the combined one-day work.
One day’s work together: \(\displaystyle\frac{1}{3}+\frac{1}{4}+\frac{1}{5}=\frac{20+15+12}{60}=\frac{47}{60}\)
Time taken: \(\displaystyle\frac{60}{47}=1\frac{13}{47}\) days