SOLUTION: How many gallons of a 3% salt solution must be mixed with a 7% salt solution to obtain 100 gallons of a 5% salt solution?
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-> SOLUTION: How many gallons of a 3% salt solution must be mixed with a 7% salt solution to obtain 100 gallons of a 5% salt solution?
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Let represent the number of gallons of 3% solution. Then the gallons of pure salt in the 3% solution must be . The number of gallons of 7% solution, given that we need 100 gallons overall, must be , and the number of gallons of pure salt in the 7% solution must be . And finally, there has to be 5 gallons of pure salt in 100 gallons of 5% solution.
If you multiply by 100 you get integer coefficients -- much neater:
