To find Theresa's percent error in her estimate of the giraffe's height, 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 case:
- Estimated Value = 18 feet
- Actual Value = 16 feet
Now, we can plug these values into the formula:
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Calculate the absolute error: \[ |\text{Estimated Value} - \text{Actual Value}| = |18 - 16| = 2 \]
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Divide the absolute error by the actual value: \[ \frac{2}{16} = 0.125 \]
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Multiply by 100 to get percent error: \[ 0.125 \times 100 = 12.5 \]
Therefore, Theresa's percent error in her estimate of the giraffe's height is 12.5%.