SOLUTION: How many gallons of a 50% saltwater solution must be added to 10 gallons of a 15% solution to obtain a 35% solution?

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Question 946574: How many gallons of a 50% saltwater solution must be added to 10 gallons of a 15% solution to obtain a 35% solution?
Found 2 solutions by stanbon, addingup:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
How many gallons of a 50% saltwater solution must be added to 10 gallons of a 15% solution to obtain a 35% solution?
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Equation:
salt + salt = salt
0.50x + 0.15*10 = 0.35(x+10)
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50x + 15*10 = 35x + 35*10
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15x = 20*10
x = 200/15
x = 13 1/3 gallons (amt. of 50% solution needed)
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Cheers,
Stan H.
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Answer by addingup(3677) About Me  (Show Source):
You can put this solution on YOUR website!
10 gallon at 15% + x gallon at 50% = 10+x gallon at 35% We will rewrite:
.15(10) + .50(x) = .35(10+x)
1.5 + .50x = 3.5 + .35x Subtract 1.5 from both sides:
.5x = 2 + .35x now subtract .35x from both sides and you get:
.15x = 2 Finally divide both sides by .15:
x = 13.33 gallon of 50% solution.