How do i solve? a chemist has 0.4 liters of an acid solution whose acid concentration is 80%. how many liters of pure water should be added to lower the concentration to 40%?

.2 litres of water should dilute the acid to 40

The question is kind of confusing. if it's asking how many variations of answers can you give. then do 4^5 for your answer.this would be something like the first question could be a and the 2nd c or first b next c etc. if you can, ask the teacher for a better confirmation of what it's asking. if i'm assuming correctly what it's asking, it's 625 different variations.