Rinnie needs to fill his exmpty fuel carried for an emergency delivery. He has to pumps that can fill the carrier in 2 hours when both used at the same time. Individually, one of the pumps takes 45 mintues less than the other to fill the empty carrier. Suddenly, he realizes that he loaned his faster pump to a friend who is presently out of town. He must rely on the slower pump to do the job. How much time will it take to fill the empty carrier with this slower pump?
If the slower pump can do the job in x minutes, we have
1/x + 1/(x-45) = 1/120