A raindrop consists of 75% water and the rest is dust. However, by the time it reaches the surface of Earth, it is left with 70% water as 2 ml water evaporates on the way. Find the original volume of the raindrop.

Download mixtures and alligations formulas for CAT, which will help a lot.

12 ml

does the evaporated 2 ml also include dust?

Before, The volume was V and the amount of water was 0.75V
After 2ml of water was lost, the volume became V-2 and the amount of water became 0.7(V-2).
This results in the equation 0.7(V-2) = 0.75V-2. Solving this will give you 12ml.

Let the original volume be x ml. It contains (3x/4) water. After evaporation, 2 ml gets lost. So now the volume becomes x-2 ml. And this x-2 ml contains 70% water. So, an equation can be formed as:
(3x/4) - 2 = [7(x-2)/10]
which will give x=12 ml. which is the original volume.

12 ml is the right answer. Can you please help with the solution @Awesh

160/3

please provide here the solution you try. BTW this is not the right answer.

30 ml