A tank contains 2760 L of pure water.
Solution that contains 0.02 kg of sugar per
liter enters the tank at the rate 5 L/min, and is thoroughly
mixed into it.
The new solution drains out of
the tank at the same rate. (a) How much sugar is in the tank at the begining? y(0)= (kg)

(b) Find the amount of sugar after t minutes. y(t)= (kg)

(c) As t becomes large, what value is y(t) approaching ? In other words, calculate the following limit.
(kg)

y(0)=0 y(t)=

(2760)*(.02)

The work

12.

A tank contains 80 kg of salt and 1000 L of water. A solution of a concentration 0.04 kg of salt per
liter enters a tank at the rate 7 L/min. The solution is mixed and drains from the tank at the same rate.

(a) What is the concentration of our solution in the tank initially? concentration = (kg/L)

(b) Find the amount of salt in the tank after 2 hours. amount = (kg)

(c) Find the concentration of salt in the solution in the tank as time approaches infinity. concentration = (kg/L)

a) 0.08 kg/L

b)

c) 0.04

The work

13.

A tank contains 50 kg of salt and 2000 L of water. Pure water enters a tank at the rate 12 L/min. The
solution is mixed and drains from the tank at the rate 6 L/min.

(a) What is the amount of salt in the tank initially? amount = (kg)

(b) Find the amount of salt in the tank after 4.5 hours. amount = (kg)

(c) Find the concentration of salt in the solution in the tank as time approaches infinity. (Assume your tank
is large enough to hold all the solution.) concentration = (kg/L)