In a mixture there is 15% of salt. When 30 liter of water is evaporated, salt becomes 20% of mixture. Find the initial quantity of mixture.

Explanation:-

Let Mixture was X initially.
Initial Salt = 15% of X = 0.15X.
Initial Water = 85% of X = 0.85X.
30 liter of water evaporated.
So, Final water = (0.85X - 30).
Now, salt rises to 20% of the mixture, it means as water dried up salt rises.

Now, Total Mixture = (0.85X -30 + 0.15X).
Final salt = 20% of(0.85X - 30 + 0.15X)

As, Initial Amount of salt = Final amount of salt, we have,

0.15X = 20% of(0.85X - 30 + 0.15X)
0.15X = 0.20X - 6.
Or, 0.5X = 6.
Thus, X = 120.

Initial amount of the mixture was 120 liter.