Question

how much pure water must be mixed with 20 liters of a 25% acid solution to reduce it to a 10% acid solution ?

Answer 1

C1V1 = C2V2

C1 will be the concentration of the original solution,
V1 will be the volume of the original solution,
C2 will be the concentration o the diluted solution, and
V2 will be the volume of diluted solution.

(25%)(20L) = (10%)V2

V2 = (25%)(20L) / (10%)

Therefore, V2 = 50L


Good luck :)