Pipe A can fill a tank in 20 minutes and pipe B in 30 minutes and pipe C can empty the same in 40 minutes. If all of them work together, find the time taken to fill the tank.
সমাধান
সঠিক উত্তর: Option A
Pipe I 20 minutes She does 1/20 job in 1 min Pipe II 30 minutes He does 1/30 of the job in 1 min Pipe III 40 minutes
It does 1/40 of the job in 1 minTogether they will do 1/20 + 1/30 - 1/40 Together they will do 7/120 of the job in 1 min So they will take 120/7 minutes= 17 1/7 minutes
