It should take about 3.25 minutes
Answer: A number increased by 8.1' .
Answer:
The answer is 4 liters.
Step-by-step explanation:
We want a final 25% solution, which means that the solvent should constitute 25 percent of all the liters of solution.
Let us call
the litres of 40% solution, so when they are added to the 12 litres of 20% solution, the total litres of the new solution are:
![x+12](https://tex.z-dn.net/?f=x%2B12)
of these liters, 25% must be the solvent:
![N=0.25(x+12)](https://tex.z-dn.net/?f=N%3D0.25%28x%2B12%29)
Now for the 40% solution, the liters of the solvent are
, and for the 20% liter solution, the liters of solve are
liters. Thus the total liters
of the solvent are
![N=0.4x+2.4](https://tex.z-dn.net/?f=N%3D0.4x%2B2.4)
Therefore
![N=0.4x+2.4=0.25(x+12)](https://tex.z-dn.net/?f=N%3D0.4x%2B2.4%3D0.25%28x%2B12%29)
![\therefore x=4\:litres](https://tex.z-dn.net/?f=%5Ctherefore%20x%3D4%5C%3Alitres)