Adam and Paul can achieve the sales target of the company in 30 days, Paul and Charles in 40 days while Charles and Adam in 60 days.
In how many days can all three of them achieve the sales target together?
Let’s say a for Adam p for Paul and c for Charles.
a + p = 1/30
p + c = 1/40
c + a = 1/60
If we sum all of them; 2(a+p+c) = 9/120 from tihs equation
=> a+p+c = 9/240
=> answer is 9/240 days = 26.6 days.