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How many liters each of a 35% acid solution and a 85% acid solution must be used to produce 50 liters of a 55% acid solution?
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Let x be the required volume of a 35% acid solution, in liters.
Then the volume of a 85% acid solution is (50-x)
The equation for the pure acid volume is
0.35x + 0.85*(50-x) = 0.55*50.
Simplify and solve:
0.35x + 42.5 - 0.85x = 27.5,
-0.5x = 27.5 - 42.5,
-0.5x = -15,
x = = 30.
Answer. 30 liters of the 35% acid solution and (50-30) = 20 liters of the 85% acid solution is needed.