Initially 10 grams of salt are dissolved into 35 liters of water. Brine with concentration of salt 4 grams per liter is added at a rate of 5 liters per minute. The tank is well mixed and drained at 5 liters per minute. Let x be the amount of salt, in grams, in the solution after t minutes have elapsed. Find a formula for the incremental change in the amount of salt, Ax, in terms of the amount of salt in the solution x and the incremental change in time At. Enter At as "Deltat". Δη = 20-Deltat grams help (formulas) Find a formula for the amount of salt, in grams, after t minutes have elapsed. t x(t) = = 140-130e 7 grams help (formulas) How long must the process continue until there are exactly 25 grams of salt in the tank? minutes help (numbers)

A tank contains 3000 gallons of pure water. Polluted water containing 2 lb of sludge per gallon enters the tank at a rate of 5 gallons/hour. The solution is thoroughly mixed and drains from the tank at a rate of 6 gallon/hour. Find a formula for the concentration of pollutants at time t. Sketch the graph of the concentration over time (you are welcome to use a graphing calculator), clearly showing the valid domain for your solution.

The air in a room 15 ft by 12 ft by 12 ft is 3% carbon monoxide. Starting at t=0, fresh air containing no carbon monoxide is blown into the room at a rate of 300 ft/min. If air in the room flows out through a vent at the same rate, when will the air in the room be 0.01% carbon monoxide? The air in the room will be 0.01% carbon monoxide after (Round to two decimal places as needed.) minutes.

The doubling period of a baterial population is 1010 minutes. At time t=80t=80 minutes, the baterial population was 70000.What was the initial population at time t=0t=0?   Find the size of the baterial population after 4 hours.