# Thirty seven wells in Tallahassee were tested in July, 1989. Thirteen of these wells were contaminated. What percent of the wells were contaminated?

Dec 21, 2016

35.1% of the wells were contaminated.

#### Explanation:

"Percent" or "%" means "out of 100" or "per 100" or $\frac{w}{100}$.

We can then write this problem as:

$13 : 37 = \frac{w}{100}$

or

$\frac{13}{37} = \frac{w}{100}$

Now we solve for $w$:

$\textcolor{red}{100} \times \frac{13}{37} = \textcolor{red}{100} \times \frac{w}{100}$

$\frac{1300}{37} = \textcolor{red}{\cancel{\textcolor{b l a c k}{100}}} \times \frac{w}{\textcolor{red}{\cancel{\textcolor{b l a c k}{100}}}}$

$\frac{1300}{37} = w$

$35.1 = w$ rounded to the nearest 10th.