In 500cmcube of alcohol solution the percentage of alcohol by volume is 80%. Find the volume of water that must be added to the solution so that the ratio of the volume of alcohol to that of water becomes 5:2?

Question

Please some one give me answer

Answer 1

working with the amount of alcohol, which remains unchanged,

.80 * 500 = 5/7 (500+x)
x = 60

check:
in 560 ml, there are 400ml alcohol, 160 ml of water

400:160 = 5:2