A can do a piece of work in 20 days, while B can do it in 15 days, with the help of C, they finished the work in 5 days. In what time would C alone do it?
A alone do work in 20 days.
B alone can do work in 15 days.
A,B,C together can do work in 5 days.
Lets suppose C alone do work in x days.
15=125+115+1x
15−3−575=1x
775=1x,x=757 days
C alone do work in 754 days or 10.71 days.