The depth of a river went from 64 feet to 56 feet. what was the percent of decrease in the water depth?

To answer the question above, determine first the decrease in the depth and then divide by the initial depth. Multiply the quotient by 100%. This is shown below.
 
            % decrease in water depth = ((64 - 56) / 64) x 100% = 12.5%

Thus, the water depth is decreased by 12.5%.