To calculate the percent error in Grace's estimate of the giraffe's height, we can use the 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 ft
- Actual Value = 16 ft
Now, plug the values into the formula:
\[ \text{Percent Error} = \left( \frac{18 - 16}{16} \right) \times 100 \]
Calculating the numerator:
\[ 18 - 16 = 2 \]
Now substitute back into the percent error formula:
\[ \text{Percent Error} = \left( \frac{2}{16} \right) \times 100 \]
Calculating the fraction:
\[ \frac{2}{16} = 0.125 \]
Now, multiply by 100 to find the percent error:
\[ \text{Percent Error} = 0.125 \times 100 = 12.5 \]
Finally, rounding to the nearest ten gives us:
\[ \text{Percent Error} \approx 10% \]
So, Grace's percent error is approximately 10%.