$A$ man travels by a car to his office at $60 \, km/h$ and returns home along the same route at $20 \, km/h$. Find the average speed of his whole journey (in $km/h$).

The average of a non-zero number and its square is $5$ times the number. The number is

The average of $5$ consecutive integers starting with $m$ is $n$. What is the average of $6$ consecutive integers starting with $(m+2)?$

The average of first three numbers is double of the fourth number. If the average of all the four numbers is $12,$ find the $4^{th}$ number.

The average age of a husband,wife,and their child $3 \text{ years}$ ago was $27 \text{ years}$,and the average age of the wife and the child $5 \text{ years}$ ago was $20 \text{ years}$. The present age of the husband is (in $\text{years}$):

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: