There is 81 litres pure milk in a container. One-third of

There is 81 litres pure milk in a container. One-third of milk is replaced by water in the container. Again one-third of mixture is extracted and equal amount of water is added. What is the ratio of milk to water in the new mixture?

Quantity of milk in the last

= 81		1 −	27		²	= 81		1 −	1		²
			81						3

= 81 ×	2	×	2	= 36
	3		3

Quantity of water in the last
= 81 – 36 = 45

∴ Ratio =	36	×	4	= 4 : 5
	45		5