In a mixture of 75ltr the ratio of milk to water is 2 1 The amount of water to be further added to t...........

Explanation:

M : W
BEFORE       2   :   1…………..(1)
AFTER         1*2:   2*2
.                   2   :     4………….(2)
multiply 2 in equation (2) to make milk same……so…..1 =25
4 = 100
100 – 25 = 75ltr

Hence, option 4 is the correct answer.