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

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Answer 1 · 2016-12-21T14:58:35

35.1% of the wells were contaminated.

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

We can then write this problem as:

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

or

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

Now we solve for $w$ $w$ :

$100 \times \frac{13}{37} = 100 \times \frac{w}{100}$ $color(red)(100) xx 13/37 = color(red)(100) xx w/100$

$1300/37 = color(red)(cancel(color(black)(100))) xx w/color(red)(cancel(color(black)(100)))$

$1300/37 = w$

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