A swimming pool had 2.5 million liters of water in it. Some water evaporated, and then the pool only had 2 million liters of water in it.
What percent of the water evaporated?
Original volume = 2.5 million liters. After evaporation, the remaining volume is 2 million liters, therefore Evaporated volume = 2.5 - 2 = 0.5 million liters.