Question

As a water quality assurance employee for local Aqua America, Inc branch record a drop in water levels from 28 feet to 7 feet at your reservoir. What is your percentage decrease?

Answer 1

7 is 1/4 of 28, so 7 is 25% of 28.
The drop from 28 to 7 is a drop of 21.
21 is 3 times 7, so 21 is 3 times 25%.

Answer: It is a 75% decrease.

Answer 2

Percentage decrease in the reservoir level is 75%.

Explanation:

Initial level of the water in the reservoir was recorded = 28 feet

Level of water at the reservoir after the drop = 7 feet

Decrease in the water level = (28 - 7) = 21 feet

Now to calculate the percentage drop we will apply the formula,

Percentage change =
`\frac{\text{Net change}}{\text{Initial level}}* 100`

=
`(21)/(28)* 100`

= 75%

Percentage decrease in the reservoir level is 75%.