Question 519297
Solution A
Amount = x ounces
Concentration = 40% = 0.4
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Solution B
Amount = 140-x ounces
Concentration = 90% = 0.9
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Final Solution
Amount = 140 ounces
Concentration = 80% = 0.8

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Amount A * Concentration A + Amount B * Concentration B = Final Amount * Final Concentration
0.4*x+0.9(140-x)=140*0.8
0.4x+126-0.9x=112
0.4x-0.9x=112-126
-0.5x=14
-0.5x/-0.5=14/-0.5
x=28
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Solution A
Amount = x = 28 ounces
Concentration = 40% = 0.4
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Solution B
Amount = 140-x = 140-28 = 112 ounces
Concentration = 90% = 0.9


She should use Solution A 28 ounces and Solution B 112 ounces to obtain a mixture of 140 ounces with 80% Salt.