A fish tank initially contains 30 liters of pure water. Brine of constant, but unknown, concentration of salt is flowing in at 3 liters per minute. The solution is mixed well and drained at 3 liters per minute.
Let be the amount of salt, in grams, in the fish tank after minutes have elapsed. Find a formula for the rate of change in the amount of salt, , in terms of the amount of salt in the solution and the unknown concentration of incoming brine .
grams/minute
Find a formula for the amount of salt, in grams, after minutes have elapsed. Your answer should be in terms of and .
grams
In 15 minutes there are 25 grams of salt in the fish tank. What is the concentration of salt in the incoming brine?
g/L
You can earn partial credit on this problem.