A, B and C can do a work in 4 days, 5 days and 10 days respectively. In how many days will they be able to do the work if they work together?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \(1\frac{9}{11}\)
A person who finishes a job in \(n\) days does \(\frac{1}{n}\) of it in one day. When people work together their one-day work is added, and the days needed for the whole job are 1 divided by that joint one-day work.
One-day work of A, B and C together \(\displaystyle =\frac{1}{4}+\frac{1}{5}+\frac{1}{10}=\frac{5+4+2}{20}=\frac{11}{20}\)
Days needed for the whole work \(\displaystyle =1\div\frac{11}{20}=\frac{20}{11}=1\frac{9}{11}\) days