A tank contains 100 gal of brine made by dissolving 60 lb of salt in water. Salt water containing 1 lb of slat per gallon runs in at the rate of 2 gal/min and the well stirred mixture runs out at the same rate of 3 gal/min. Find the amount of salt in the tank after 30 minutes.

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anonymous · Answer

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anonymous · Answer

@henrykidd, so the mixture runs out at the same rate? Meaning 2 or 3 gal/min?

In any case, you'll the following equation:
$$y'=2-\left(\frac{y}{100-(\text{(rate out)}-\text{(rate in)})t}\right)(\text{rate of flowing out})$$