You have 15 liters of 75% antifreeze.
How many liters of 95% antifreeze must be mixed with this to make an 80% antifreeze solution?
We will only need one equation for this.
We have 15 liters of 75% antifreeze to which we will add several liters (or "x") of 95% antifreeze to make an 80% antifreeze solution.
.75 * 15 + .95x = .80 * (15 + x)
where (15 + x) is the volume of the 80% antifreeze solution.
11.25 + .95x = 12 + .80x
.15x = .75
x = 5 liters
C) Calculating concentration of final solution
Example:
15 liters of 75% antifreeze is mixed with 5 liters of 95% antifreeze.
What is the antifreeze percentage of the final solution?
Using the calculator, we click "A" then enter
Solution 1 Volume 15
Solution 1 Concentration 75
Solution 2 Volume 5
Solution 2 Concentration 95
Clicking "Calculate" we see the answer is:
Concentration of Final Solution 80
Without using the calculator:
You mix 15 liters of 75% antifreeze with 5 liters of 95% antifreeze.
What is the antifreeze percentage of the final solution?
Let us calculate the volume of antifreeze in the final solution.
15 * .75 = 11.25 liters of antifreeze.
5 * .95 = 4.75 liters of antifreeze.
Equals 16 liters of antifreeze.
The total volume of the final solution = 15 + 5 = 20 liters.
Therefore, the antifreeze percentage = 16 liters / 20 total liters = 80 per cent.