$A$ 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:

The average of five consecutive positive integers is $n$. If the next two integers are also included,the average of all these integers will

If the mean of $a, b, c$ is $M$ and $ab + bc + ca = 0$,then the mean of $a^2, b^2, c^2$ is

The average age of $8$ members of a group is $40 \text{ years}$. The age of $1$ member is $55 \text{ years}$. After his retirement,a new member of age $39 \text{ years}$ joins the group. What is the effect of this replacement on the average age of the group?

The sum of the ages of father and son at present is $33 \, \text{years}$. Two years ago, the product of their ages was $28 \, \text{years}$. What is the age of the father and the son (in $\text{years}$)?

The average of $25$ consecutive odd integers is $55$. The highest of these integers is