Question

Situation 1
A tank initially contains 100 gal of pure water. Starting at time t = 0, a brine containing 6lb of dissolved
salt per gallon flows into the tank at the rate of 8gal/min is kept uniform by stirring and the well-stirred
mixture simultaneously flows out of the tank at a slower rate of 4gal/min.
1. How much salt is in the tank at the end of 20 min?
2. When is there 50 lb of salt in the tank?

Answer 1

1. 6lb/gal*(8-4)gal/min= 24lb/min 24lb/min*20min= 480lb
2. (20min*50lb)/480lb= 2.08min