To calculate the percent error in their prediction, we first need to find the difference between the predicted number of attendees (275) and the actual number of attendees (265).
275 - 265 = 10
Next, we need to calculate the percent error by taking the absolute value of the difference (10) divided by the predicted number of attendees (275), and then multiplying by 100 to get the percentage.
(10/275) * 100 = 3.63636363636%
Rounded to the nearest hundredth percent, the percent error in their prediction is 3.63%.
Therefore, the correct response is:
3.63%