SOLUTION: initially, a tank contains 20 gallons of 30% antifreeze solution. how many gallans of 80% antifreeze solution should be added to the tank in order to have the concentration of the

Question 303510: initially, a tank contains 20 gallons of 30% antifreeze solution. how many gallans of 80% antifreeze solution should be added to the tank in order to have the concentration of the antifreeze in the tank increase to 50%?
Found 2 solutions by richwmiller, stanbon:
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
You didn't say how big the tank is.
.3*20+.8x=.5(20+x)
6+.8x=10+.5x
.3x=4
x=4/.3
x=40/3
x=13 1/3
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
initially, a tank contains 20 gallons of 30% antifreeze solution. how many gallans of 80% antifreeze solution should be added to the tank in order to have the concentration of the antifreeze in the tank increase to 50%?
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Equation:
alcohol + alcohol = alcohol
0.30*20 + 0.80*x = 0.50(20+x)
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Multiply thru by 100 and solve for "x":
30*20 + 80x = 50*20 + 50x
30x = 20*20
x = (2/3)*20
x = 13 1/3 gallons (amt of 80% antifreeze needed in the mixture)
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Cheers,
Stan H.
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