If there are 400 cubic centimeters of a chemical in 1 liter of solution (1000 cc=1 liter), how many cubic centimeters of water must be added to dilute it to a 25% solution?

Answer 1

If the chemical occupies 400 of the 1000 ml of solution, then it is a 40% solution.

25% is 5/8 as strong, so the volume of solution has to grow by a factor of 8/5, to 1600 ml.