I'm not sure how to do this problem...

Question

Initially, a tank contains 20 gallons of 30% antifreeze solution. How many gallons of an 80% antifreeze solution should be added to the tank in order to increase the concentration of the antifreeze in the tank to 50%?

Answer 1

Allow x = # gallons added of the 80% solution.

 

We can calculate the overall concentration via:

 

   20(.30) + x(.80) = (x+20)(.50)  and then solve algebraically

 

6+.8x = .5x +10

 

.3x = 4

 

x = 4/.3 = 13 1/3 gallons