DATE:23-11-2017
Q)
A and B can finish a piece of work in 40 days. B and C in 60 days and C and A in 80 days. In how many days will A alone finish the job?

Ans:  96 days(Option-3)

SOLUTION:
1)Work done by A and B each day=(1/40)
2)Work done by B and C each day=(1/60)
3)Work done by A and C each day=(1/80)
4)Work done by A in each day=Work done by(A+B+C)each day - Work done by(B+C) each day
5)Work done by (A+B+C) each day=(1/40+1/60+1/80)/2
6)Work done by A alone in each day =.  (1/40+1/60+1/80)/2-(1/60)
The denominator gives number of days A took to complete the work=96 days