# Homework Help: Am I setting this diff eq up correctly?

1. Feb 15, 2005

### kdinser

The problem:
A large tank is partially filled with 100 gallons of fluid in which 10 pounds of salt is dissolved. Brine containing .5 pounds of salt per gallon is pumped into the tank at a rate of 6 gal/min. The well mixed solution is then pumped out at a rate of 4 gal/min. Find the number of pounds of salt in the tank after 30 minutes.

I've tried this problem 4 times and before I try it again, I want to varifie that I'm setting it correctly.

A=pounds of salt
t=time in minutes

$$\frac{dA}{dt}=3-\frac{4A}{100+2t}$$

Does this look right?

2. Feb 15, 2005

### Staff: Mentor

It looks right to me.