3 litres of water is added to 15 litres of a mixture of

3 litres of water is added to 15 litres of a mixture of a 20% solution of alcohol in water. The strength of alcohol is now ?

Alcohol in 15 litres =(20 x 15)/100 litres = 3 litres
Now, alcohol in 18 litres = 3 litres

∴ strength of alcohal =(3/18) x 100 % = 16²/₃%