In How much Time All the Three Finish Work?
Answer: (b) 9 days
A person can do a piece of work in 15 days.
Therefore A person can do work in a day = 1/15
B person can do same work in 6 days.
Therefore B person can do work in a day = 1/6
C person can do same work in 10 days.
Therefore c person can do work in a day = 1/10
All together can do work = 1/15 + 1/6 + 1/10 = 10/30
Hence, the altogether can do piece of work in 3 days.
All together can do three times of work = 3 x 3 = 9 days.