The average of the first nine prime numbers is

The average of five consecutive odd integers is $27$. What is the product of the first and the last number?

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 of $7$ numbers is $5$. If the average of the first six of these numbers is $4$,the seventh number is:

The average weight of a group of $20$ boys was calculated to be $89.4 \, kg$ and it was later discovered that one weight was misread as $78 \, kg$ instead of $87 \, kg$. The correct average weight is (in $kg$).

Of the three numbers whose average is $60$,the first is one-fourth of the sum of the others. The first number is