- #1

Fragster

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## Homework Statement

A tank initially contains 200 gallons of fresh water, but then a salt solution of unknown concentration lb/gal is poured into the tank at 2 gal/min. The well-stirred mixture flows out of the tank at the same rate. After 120 minutes, the concentration of salt in the tank is 1.4 lb/gal. What is the concentration (in lb/gal) of the entering brine?

## Homework Equations

Net rate of salt solution = rate of incoming salt solution - rate of outgoing salt solution

## The Attempt at a Solution

I actually have the solution

280/(200-200(e^(-6/5))) or roughly, 2

but I cannot remember for the life of me how I got it :/

I think the biggest problem I have with the problem is the relationship between the rate of salt going in (x) and the net rate of salt.