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

It rained as much on Wednesday as on all the other days of the week combined. If the average rainfall for the whole week was $3 \, cm$,then how much did it rain on Wednesday? (in $cm$)

Average age of $15$ students of a class is $15 \text{ years}$. Out of these,the average age of $5$ students is $14 \text{ years}$ and that of the other $9$ students is $16 \text{ years}$. The age of the $15^{th}$ student is (in $\text{years}$):

The sum of eight consecutive numbers of Set $A$ is $376$. What is the sum of $5$ consecutive numbers of another set if its minimum number is $15$ ahead of the average of Set $A$?

The average age of $35$ students in a class is $16$ years. The average age of $21$ students is $14$ years. What is the average age of the remaining $14$ students (in years)?

The average age of $30$ girls is $13$ years. The average age of the first $18$ girls is $15$ years. Find the average age of the remaining $12$ girls.