Question

A salt solution of 15 litres contains 20% salt.How much water must you add to salt solution in order to dilute it 15% salt?

Answer 1

you want 3/4 the concentration, so you must have 4/3 the volume.

Answer 2

Or use the reliable c1v1 = c2v2
20%*15L = 15%*L
L =?

Answer 3

c1v1=c2v2
20%*15L=15%*L
20/100*15=15/100*L
3=3/20*L
L=3*20/3
L=20Ltrs

Answer 4

You must add 75 liters.

:)