Question

The ratio of milk and water in a container is 7: 5. If 9 liter of mixture is removed from the container and filled with water, the ratio of milk and water becomes 7: 9.How much milk will you initially have in the container ?​

Answer 1

Let, the initial amount of milk and water be 7x and 5x respectively

amount of milk removed=(7/12)*9=21/4

amount of water removed=(5/12)*9=15/4

7x-21/4=amount of milk left

5x-15/4+9=amount of water you have after taking out 15/4 water and adding 9 L of water

According to question,

(7x-21/4)/(5x-15/4+9)=7:9

or,(28x-21/4)/(20x+21/4)=7/9

or,9(28x-21)=7(20x+21)

or,252x-189)=140x+147

or,252x-140x=189+147

or,112x=336

or,x=336/112

or,x=3

So, the initial amount of milk=7×3

=21 liter