SOLUTION: A chemical mixing tank can be filled by two hoses. One requires 42 min to fill the tank , and the other 30 min . If both hoses are used, how much time is needed to fill the tank?

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A chemical mixing tank can be filled by two hoses. One requires 42 min to fill the tank , and the other 30 min . If both hoses are used, how much time is needed to fill the tank?      Log On


   

Question 331746: A chemical mixing tank can be filled by two hoses. One requires 42 min to fill the tank , and the other 30 min . If both hoses are used, how much time is needed to fill the tank?
Answer by mananth(16949) About Me  (Show Source):
You can put this solution on YOUR website!
one hose takes 42 minutes
so it does 1/42 of the job in 1 minute.
..
the other fills in 30 minutes
so it does 1/30 of the job in 1 minute
.
together they can do 1/30+1/42 of the job in 1 minute
..
30+42/ 32*40 of the job in 1 minute
72/1280
So they will together fill the tank in 1280/72= 17.7 minutes