Final answer:
To find the attendance on Friday, we added the known attendances from Monday to Thursday and subtracted the sum from the total weekly attendance, based on the mean attendance of 40 over 5 days, resulting in 57 attendees on Friday.
Step-by-step explanation:
To calculate the attendance on Friday, we need to use the information provided about the mean attendance and the known attendances on the other days.
The mean attendance of 40 for all five days means the total sum of attendances from Monday to Friday is 5 × 40 = 200.
From the information given, we know the attendance on Monday (28), Tuesday (37), Wednesday (35), and Thursday (43).
The total attendance from Monday to Thursday is 28 + 37 + 35 + 43 = 143.
Since the total attendance for the whole week is 200, we subtract the total attendance from Monday to Thursday from this figure to find the attendance on Friday: 200 - 143 = 57.
Therefore, the attendance on Friday is 57.