A tank contains 2000 L of pure water. Brine that contains 15 g of salt per liter of water is pumped into the tank at a rate of 25 L/min. The concentration of salt after t minutes (in grams per liter) is C(t) = 15t/80 + t. As t → ∞, what does the concentration approach?

Answer 1

clearly you must have meant
C(t)=15t/(80+t) which --> 15

I am troubled by the fact that the equation for C(t) does not reflect the data given in the words. Also, at some point the tank will overflow, so having t unbounded is not realistic.