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 $3$ persons is $65 \, kg$. If a fourth person having a weight of $45 \, kg$ joins the group,what is the average weight of the group? (in $kg$)

The average of odd numbers up to $100$ is?

$A$ batsman makes a score of $81$ runs in the $16^{\text{th}}$ match and thus increases his average runs per match by $3$. What is his average after the $16^{\text{th}}$ match?

The average of $11$ results is $50$. If the average of the first six results is $49$ and that of the last six is $52$,the sixth result is:

The average of prime numbers between $1$ and $20$ is