Question 99723
If first pipe fills the whole tank in 30 minutes, then in one it fills {{{1/30}}} and if second one empties the tank in 50 minutes then it empties {{{1/50}}} of tank in one minute. We can write {{{1/30-1/50}}},this expresses the state of tank after 1 minute.We can subtract and get {{{5/150-3/150}}} = {{{2/150}}} after 1 minute {{{2/150}}} of tank will be filled. By dividing 150 by 2 we can determine how long will it take to fill the whole tank.I takes 75 minutes.