Question

since 1970, implementations of the clean air act and technological advances have greatly improved air quality in the united states. the data below were published in the 2020 environmental protection agencys our nations air report.
air pollutant concentration in 1980 (ppm) concentration in 2019 (ppm)
no2 111 42.0
co 9 1.3
so2 157 13.0
calculate the percent decrease of no2 concentration between 1980 to 2019.
round your answer to the nearest whole percentage.
references: epa.gov. nitrogen dioxide. carbon monoxide. sulfur dioxide.

Explanation:

Step1: Find the amount of decrease

The formula for the amount of decrease is the initial value minus the final value. For $\text{NO}_2$, the initial concentration in 1980 is $111$ ppm and the final concentration in 2019 is $42.0$ ppm. So the amount of decrease $d=111 - 42.0=69$.

Step2: Calculate the percent - decrease

The formula for percent - decrease is $\text{Percent Decrease}=\frac{\text{Amount of Decrease}}{\text{Initial Amount}}\times100\%$. Substitute the values we found: $\text{Percent Decrease}=\frac{69}{111}\times 100\%$.
$\frac{69}{111}\times100\%=\frac{6900}{111}\% \approx 62.16\%$.
Rounding to the nearest whole percentage gives $62\%$.

Answer:

$62$