A can do a piece of work in 6 days. B can do it in 9 days. With the assistance of C they completed the work in 3 days. In how many days can C alone do the work ?

18

A = 6 days, B = 9 days, A + B+ C = 3 days,

⇒ Therefore, C = 1 (Efficiency)

⇒ Time required by C to complete total work alone = \(\frac{18}{1}\) = 18 days   ..(\(\frac{Work}{Efficiency}\) = Time)