Posted by **Anonymous** on Saturday, March 1, 2008 at 11:20pm.

Beginning with a tank containing 8075 gallons of gasoline, more gas is added at a rate of 5 gallons per minute, while alcohol is added at a rate of 10 gallons per minute. When the mixture is 10% alcohol, how many gallons of the mixture are in the tank?

Is there an easier way to do it than writing out every number and making a table, I'm pretty sure there is, but I can't remember it.

- Math -
**drwls**, Sunday, March 2, 2008 at 12:30am
An easier way is algebra.

Beginning at time t=0, the amount of gasoline in the tank In gallons) is

G = 8075 + 5 t

and the amount of alcohol is

A = 10 t.

The mixture is 10% alcohol when

A /(G + A) = 0.1 or

G = 9 A.

So, solve this equation for t:

8075 + 5 t = 90 t

85t = 8075

t = 95 minutes.

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