SSC CHSL 15 Nov 2015 Shift 1 Paper

Ratio of milk and water in 20 litres mixture = 3:1
⇒ Quantity of milk = $\frac{3}{\left(3+1\right)}\times 20=15$ litres
⇒ Quantity of water = $20-15=5$ litres
Let amount of milk added = $\mathit{x}$ litres
According to ques,
⇒ $\frac{15+\mathit{x}}{5}=\frac{4}{1}$
⇒ $15+\mathit{x}=20$
⇒ $\mathit{x}=20-15=5$
∴ The amount of milk to be added to the mixture so as to have milk and water in the ratio 4 :1 = 5 litres