explanation please
_________________

If you like my post, consider giving me KUDOS

We can let 3x = the amount of water and 5x = the amount of the liquid chemical originally in the mixture. We create the equation:

3x + 5x = 40

8x = 40

x = 5

So the amount of water originally in the mixture is 3(5) = 15 liters, and the original amount of the liquid chemical in the mixture is 5(5) = 25 liters. Since 20 percent of the initial quantity of water evaporated during a 10-day period, 0.2(15) = 3 liters of water evaporated during this period. Likewise, since 50 percent of the initial quantity of the liquid chemical evaporated during the same period, 0.5(25) = 12.5 liters of liquid chemical evaporated. Therefore, 3 + 12.5 = 15.5 liters of the original 40 liters of the mixture evaporated, which is 15.5/40 = 0.3875 = 38.75% of the mixture.

Answer: C
_________________