SOLUTION: 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 have the concentration of t

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Question 263828: 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 have the concentration of the antifreeze in the tank increase to 50%?
Answer by ptaylor(2198) About Me  (Show Source):
You can put this solution on YOUR website!

Let x=amount of 80% antifreeze needed
Initially the amount of pure antifreeze in the tank =0.30*20=6 gal. If we increase the pure antifreeze in the tank by 50% we will need to have have 6+3=9 gal of pure antifreeze((9-6)/6=50% increase). In other words, we need to use enough of the 80% antifreeze to get 3 gal of pure antifreeze. So our equation to solve is:
0.80x=3
x=3.75 gal---needs to be added to the tank
CK
20*0.30+3.75*0.80=9
6+3=9
9=9
Hope this helps---ptaylor