We find the volume of alcohol in 40 liters of solution.
We multiply the volume of the solution by the percentage of alcohol content.
40 * 80% / 100% = 40 * 0.8 = 32 liters of alcohol.
Since this volume of alcohol should correspond to 70% in the new solution, we find the volume of the new solution.
Divide 32 liters of alcohol by 70%.
32/70% = 32 / 0.7 = 45.71 liters.
From this it follows that it is necessary to add to the initial solution:
45.71 – 40 = 5.71 liters of water.
Answer: You need to add 5.71 liters.
One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.