SOLUTION: How much water should be added to 30 gallons of a solution that is 70% antifreeze in order to get a mixture that is 60% antifreeze?

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Question 16261: How much water should be added to 30 gallons of a solution that is 70% antifreeze in order to get a mixture that is 60% antifreeze?
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Here's one approach: the 30 gallons of 70% antifreeze solution is 30% water and you want to make a solution that is 60% antifreeze and 40% water. So you will add x gallons of water to the 30% water solution.
Change the percents to their decimal equivalents.
30%280.3%29+%2B+x+=+%2830+%2B+x%29%280.4%29 Simplify and solve for x, the number of gallons of water to be added.
9+%2B+x+=+12+%2B+0.4x Subtract 0.4x from both sides.
9+%2B+0.6x+=+12 Subtract 9 from both sides.
0.6x+=+3 Finally, divide both sides by 0.6
x+=+5
You will need to add 5 gallons of water to the 30 gallons of 70% antifreeze solution to make 35 gallons of 60% antifreeze solution.
Check:
30%280.3%29%2B+5+=+35%280.4%29
9+%2B+5+=+14