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 ⇒
(4x)
(9x+20)
=
1
3
⇒ 12x = 9x + 20 ⇒ 3x = 20, x=
20
3
Now the initial quantity of water in the mixture =9×(
20
3
)=60L ∴ Initial quantity of water in the mixture is 60L.