A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is:
Answer: D
Since the month begins with a Sunday, to there will be five Sundays in the month.
Required average
\(\left( \dfrac {510 \times 5 + 240 \times 25}{30} \right)\\
=\dfrac{8550}{30}\\
=285\)