In a mixture of 25 litres the ratio of acid to water is 4 : 1. Another 3 litres of water of water is added to the mixture. The ratio of acid to water in the new mixture is = ?

$$\eqalign{ & {\text{Acid}}:{\text{Water}} \cr & \,\,\,\,\,4\,\,\,\,\,:\,\,\,\,\,\,\,1 \cr & {\text{Let }}4x + x = 5x \cr & \because 4x + x = 25 \cr & \Rightarrow x = 5 \cr & \therefore {\text{Acid }} = {\text{ }}5 \times 4 = 20 \cr & {\text{Water }} = 5 \times 1 = 5 \cr & \therefore {\text{3 Litres water is added }} \cr & {\text{So, new quantity of water}} \cr & = 5 + 3 = 8 \cr & \therefore {\text{Acid}}:{\text{Water}} \cr & \,\,\,\,\,\,\,\,\,{\text{20}}\,\,\,:\,\,\,\,\,\,\,8 \cr & \,\,\,\,\,\,\,\,\,\,\,5\,\,\,\,:\,\,\,\,\,\,\,2 \cr} $$