To calculate Teresa's percent error in estimating the height of the giraffe, we can use the formula for percent error, which is given by:
\[ \text{Percent Error} = \left( \frac{|\text{Estimated Value} - \text{Actual Value}|}{\text{Actual Value}} \right) \times 100% \]
In this scenario, the estimated height of the giraffe is 18 feet, while the actual height is 16 feet. First, we need to find the absolute error, which is the difference between the estimated value and the actual value:
\[ |\text{Estimated Value} - \text{Actual Value}| = |18 - 16| = 2 \text{ feet} \]
Next, we will plug the absolute error and the actual height into the percent error formula:
\[ \text{Percent Error} = \left( \frac{2 \text{ feet}}{16 \text{ feet}} \right) \times 100% \]
Calculating the fraction:
\[ \frac{2}{16} = 0.125 \]
Now, we multiply by 100 to convert this to a percentage:
\[ \text{Percent Error} = 0.125 \times 100% = 12.5% \]
Thus, Teresa’s percent error in estimating the giraffe's height is 12.5%, which indicates that her estimate was 12.5% higher than the actual height. Rounding to the nearest tenth, the final answer remains 12.5%.