To find Teresa's percent error in her height estimate of the giraffe, we can use the following formula for percent error:
\[ \text{Percent Error} = \left( \frac{|\text{Estimated Value} - \text{Actual Value}|}{\text{Actual Value}} \right) \times 100 \]
In this scenario:
- Estimated Value = 18 feet
- Actual Value = 16 feet
First, calculate the absolute error:
\[ |\text{Estimated Value} - \text{Actual Value}| = |18 - 16| = 2 \text{ feet} \]
Next, substitute the values into the percent error formula:
\[ \text{Percent Error} = \left( \frac{2}{16} \right) \times 100 \]
Calculate the fraction:
\[ \frac{2}{16} = 0.125 \]
Now, multiply by 100 to convert it to a percentage:
\[ 0.125 \times 100 = 12.5 \]
Finally, rounding to the nearest tenth gives us:
\[ \text{Percent Error} \approx 12.5% \]
Thus, Teresa's percent error in her estimate of the giraffe's height is 12.5%.