Question

in a mixture of 126 kg of milk and water,milk and water are in the ratio 5:2 . How much water must be added to make this ratio 3:2

Answer 1

In the original mass of 126 kg of the mixture there are 7 (= 5 + 2) equal parts (masses). Hence, the milk contents is  = 5*18 = 90 kg, and water contents is  = 2*18 = 36 kg. OK. Next, the final mixture, having 90 kg of milk, must contain  = 30*2 = 60 kg ow water to provide the ratio = . Hence, 60 - 36 = 24 kg of water must be added to the original mixture to satisfy the problem requirements.
Answer. 24 kg of water must be added to the original mixture. 

Answer 2

Milk + Water= 126 kg

5 : 2 (RATIO)

so milk and water = 126/7 = 18

Milk = 18*5 = 90 kg

Water= 18*2 = 36 kg

so 90:36 = 5:2

Next, the final mixture, having 90 kg of milk, must contain 90/3 = 2

so 30*2 = 60 kg ow water to provide the ratio 3:2

so 36 + ? = 60

60 - 36 = 24

and so 24 + 36 = 60

and results in 90:60 that equals to 3:2

(Divide it you will get 3:2)

Hence, 24 kg of water must be added to the original mixture to get ratio 3:2