At noon, a tank contained 20 cm of water. After several hours, it contained 18 cm of water. What is the percent decrease of water in the tank?
To find the percent decrease in water, we need to calculate the difference in water level and then express it as a percentage of the original water level.
Initial water level = 20 cm
Final water level = 18 cm
Difference in water level = 20 cm - 18 cm = 2 cm
Percent decrease = (2 cm / 20 cm) x 100% = 10%
Therefore, the water level in the tank decreased by 10%.