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the7joker7
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Homework Statement
A tank contains 90 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.
Find the amount of salt in the tank after 1.5 hours.
Homework Equations
Assorted Calculus stuff.
The Attempt at a Solution
rate in = (.045kg per L)(12L per min) = .54kg/min
rate out = (y(t)/2000 kg per L)(6L per min) = (y(t))/(333.33)
dy/dt = .54 - ((y(t))/333.33) = (180 - y(t))/333.33
int(dy/(180 - y)) = int(dt/333.33)
-ln(180 - y) = t/333.33 + C
y(0) = 90
So -ln(90) = C
-ln(180 - y) = t/333.33 - ln(90)
180 - y = 90e^(-t/333.33)
y(t) = 180 - 90e^(t/333.33)
y(90) = 62.103
Actual Answer:
70.8661417323