SOLUTION: A hospital staff mixed a 75% disinfectant solution with a 25% disinfectant solution. How many liters of each were used to make 20L of a 40% disinfectant solution?

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Question 902532: A hospital staff mixed a 75% disinfectant solution with a 25% disinfectant solution. How many liters of each were used to make 20L of a 40% disinfectant solution?
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
a+b=20,
0.75*a+0.25*b=0.4*20
a=20-b
0.75*(20-b)+0.25*b=8
15-0.75b+0.25*b=8
-0.5*b=-7
b=14
a=20-b
a=6 liter at 75% b=14 liter at 25%
check
0.75*6+0.25*14=0.4*20
4.5+3.5=8
8=8
ok