One-third of a number is 7. Find the number.
2 answers:
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Answer:
Step-by-step explanation:
Given that a large mixing tank initially holds 400 gallons of water in which 70 pounds of salt have been dissolved. Pure water is pumped into the tank at a rate of 4 gal/min, and when the solution is well stirred, it is then pumped out at the same rate.
Let Q(t) be the quantity of salt at time t.
Q(0) = 70 pounds
Inflow of water = outflow = 4 gal/min
So resulting volume of tank at time t = 400 gallons
Rate of change of salt = inflow - outflow
= 0 -
i.e.
This is a variable separable equation
Use when t =0 Q = 70
A =70
So A(t) = Q(t) = and
A(0) = Q(0) = 70 lbs.