In two containers A and B, milk and water are in the ratio 4 : 5 and 5 : 1 respectively. In what ratio both the quantity of mixture should be mixed together so that in the new mixture of ratio of milk and water will becomes 5 : 4.

5 : 2

        Milk   :   Water

A ⇒     4    :     5     ⇒ 9  (× 2 = 18)

B ⇒     5    :     1     ⇒ 6  (× 3 = 18)

A+B ⇒ 5    :     4     ⇒ 9  (× 2 = 18)

Make all quantity equal and use allegation method:

Therefore, the mixture should be mixed in the ratio 5 : 2.