The average of the first nine prime numbers is:

If the mean of $5$ observations $x, x+2, x+4, x+6$ and $x+8$ is $11,$ then the mean of the last three observations is

The average weight of $3$ men $A, B$ and $C$ is $84 \, kg$. Another man,$D$,joins the group,and the average weight becomes $80 \, kg$. If another man,$E$,whose weight is $3 \, kg$ more than that of $D$,replaces $A$,then the average weight of $B, C, D$ and $E$ becomes $79 \, kg$. The weight of $A$ is (in $kg$):

In a family,the average age of father and mother is $38 \text{ years}$,whereas the average age of father,mother,and their only daughter is $28 \text{ years}$. Then,the age of the daughter is? (in $\text{years}$)

The average temperature of the first $4 \, \text{days}$ of a week is $38.6^{\circ} \text{C}$ and that of the last $4 \, \text{days}$ is $40.3^{\circ} \text{C}$. If the average temperature of the entire week is $39.1^{\circ} \text{C}$, find the temperature on the $4^{th} \, \text{day}$ (in $^{\circ} \text{C}$).

$A$ man spends $Rs. 1800$ monthly on an average for the first four months and $Rs. 2000$ monthly for the next eight months and saves $Rs. 5600$ a year. His average monthly income is (in $Rs.$)