AFCAT Model Paper 8

Given: The initial and the final ratio of milk and water in a given mixture are 4∶9 and 1∶3. 20 L of water is added to this mixture. Calculation: Let the initial quantity of milk and water in the mixture be 4x, 9x After adding 20 L of water the ratio becomes 1:3 ⇒ $\frac{4x}{9x+20}=\frac{1}{3}$ ⇒ 12x = 9x + 20 ⇒ 3x = 20, $x = \frac{20}{3}$ Now the initial quantity of water in the mixture $= 9\times\frac{20}{3} = 60\,\text{L}$ ∴ Initial quantity of water in the mixture is 60L.