Solution:

Given: Ratio of Milk to Water in 1st mixture = 3 : 2

Ratio of Milk to Water in 2nd mixture = 7 : 3

Ratio of Milk to Water in 3rd mixture = 2 : 5

Concept used: Ratio of Milk to Water in final mixture = (Milk in 1st mixture + Milk in 2nd mixture + Milk in 3rd mixture) : (Water in 1st mixture + Water in 2nd mixture + Water in 3rd mixture)

Calculation: Let the quantity of each mixture be ‘x’

Then quantity of Milk after mixing is {(3/5) + (7/10) + (2/7)} x

⇒ {(42 + 49 + 20)/70} x

⇒ (111/70) x

and quantity of water after mixing is {(2/5) + (3/10) + (5/7)} x

⇒ {(28 + 21 + 50)/70} x

⇒ (99/70) x

Ratio of Milk and Water in final mixture = (111/70) x : (99/70) x

⇒ 111 : 99

∴ 37 : 33