Five years ago,the average age of a husband and wife was $23 \text{ years}$. Today,the average age of the husband,wife,and child is $20 \text{ years}$. How old is the child in years?

The average of $6$ numbers is $20$. If one number is removed, the average becomes $15$. What is the number removed?

The average temperature for Monday,Tuesday,Wednesday and Thursday was $48^{\circ}$. The average temperature for Tuesday,Wednesday,Thursday and Friday was $52^{\circ}$. If the temperature on Monday was $42^{\circ}$,then the temperature on Friday was (in $degrees$):

There are $6$ consecutive odd numbers in increasing order. The difference between the average of the squares of the first $4$ numbers and the last $4$ numbers is $64$. If the sum of the squares of the first and the last element is $178$,then the average of all the $6$ numbers is:

The average of the first $25$ numbers is $10$ and the average of the next $25$ numbers is $12$. The average of all $50$ numbers is:

The average marks of students in an examination was $65$. It was later found that the marks of one student had been wrongly entered as $83$ instead of $38$. If there were $50$ students, what is the correct average?