Answer:
The 70% mixture makes up 0.7 liters of the solution whereas the 60% mixture makes up 2.8 liters of the solution.
Step-by-step explanation:
Let us have x liters of the .7 mixture and y liters of the .6 mixture.
We want total liters to be 3.5 which means we need x+y=3.5 . I don't like the decimal in the equation so I'm going to multiply both sides by 10: 10x+10y=35
We also need the .7x+.6y=.62(3.5) . I hate the decimal business going on in this question so I'm going to multiply by 1000 which gives 700x+600y=62(35) .
So we have the system
700x+600y=62(35)
10x+10y=35
I'm going to setup this up for linear combination/elimination.
Multiply bottom equation by 60.
700x+600y=62(35)
600x+600y=60(35)
Subtract equations (bottom from top):
(700-600)x+(600-600)y=35(62-60)
Simplify:
100x+0y=35(2)
100x=70
Divide both sides by 100:
x=70/100
x=7/10
Going back to x+y=3.5 along with x=7/10 or .7 liters to find y.
y=3.5-x with x=.7
y=3.5-0.7
y=2.8
The 70% mixture makes up 0.7 liters of the solution whereas the 60% mixture makes up 2.8 liters of the solution.
Pic added.
Another way to do problem:
.7x+.6(3.5-x)=.62(3.5)
Multiply and distribute:
.7x+2.1-.6x=2.17
Combine like terms on left:
.1x+2.1=2.17
Subtract 2.1 on both sides:
.1x=.07
Multiply both sides by 10:
x=0.7 liters
Now the other acid solution is 3.5-0.7 which is 2.8 litera.
