To calculate the percent error in Julian and Brittany's prediction, we can use the formula for percent error:
\[ \text{Percent Error} = \left( \frac{\text{Absolute Error}}{\text{Actual Value}} \right) \times 100 \]
Step 1: Determine the actual value and predicted value.
- Actual value (number of attendees) = 265
- Predicted value (number of attendees they expected) = 275
Step 2: Calculate the absolute error.
\[ \text{Absolute Error} = |\text{Predicted Value} - \text{Actual Value}| = |275 - 265| = 10 \]
Step 3: Substitute the values into the percent error formula.
\[ \text{Percent Error} = \left( \frac{10}{265} \right) \times 100 \]
Step 4: Perform the calculation.
\[ \text{Percent Error} \approx \left( \frac{10}{265} \right) \times 100 \approx 3.77 \]
Step 5: Round the percent error to the nearest 100%.
Since 3.77% rounds to 4%, the final answer is:
\[ \text{Percent Error} \approx 4% \]
Thus, the percent error in their prediction is approximately 4%.