SOLUTION: a worker needs to form 12 gallons of 70% ammonia solution to strip wax from some floors. He has one solution of 30% ammonia and another solution of 90% ammonia. How many gallons of

Question 598912: a worker needs to form 12 gallons of 70% ammonia solution to strip wax from some floors. He has one solution of 30% ammonia and another solution of 90% ammonia. How many gallons of the 90% solution should he use in the mixture?
Found 2 solutions by stanbon, josmiceli:
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
a worker needs to form 12 gallons of 70% ammonia solution to strip wax from some floors. He has one solution of 30% ammonia and another solution of 90% ammonia. How many gallons of the 90% solution should he use in the mixture?
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Equation:
ammonia + ammonia = ammonia
0.30x + 0.90(12-x) = 0.70*12
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30x + 90*12 - 90x = 70*12
-60x = -20*12
x = 4 gallons (amt. of 30% solution needed)
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12-x = 8 gallons (amt. of 90% solution needed)
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Cheers,
Stan H.
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = gallons of 30% mixture needed
Let = gallons of 90% mixture needed
given:
= gallons of ammonia in 30% mixture
= gallons of ammonia in 90% mixture
-----------
(1)
(2)
-----------
(2)
(2)
(2)
Multiply both sides of (1) by and
subtract (1) from (2)
(2)
(1)

and, since
(1)
(1)
(1)
8 gallons of the 90% mixture are needed
check:
(2)
(2)
(2)
(2)
OK
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