The average age of the boys in a class is $16 \text{ years}$ and that of the girls is $15 \text{ years}$. The average age for the whole class is:

$A$ batsman has a certain average in $11$ innings. In the $12^{\text{th}}$ innings,he scores $90$ runs and his average decreases by $5$. After the $12^{\text{th}}$ innings,what is his average?

The average temperature from Monday to Thursday is $48^{\circ} C$ and from Tuesday to Friday,the average temperature is $52^{\circ} C$. If the temperature on Monday is $42^{\circ} C$,what was the temperature on Friday in $^{\circ} C$?

$A$ person travelled from one place to another at an average speed of $40 \, km/h$ and back to the original place at an average speed of $50 \, km/h$. What is his average speed in $km/h$ during the entire trip?

Out of four numbers,the average of the first three is $16$ and that of the last three is $15$. If the last number is $20$,then the first number is:

The daily earnings of a taxi driver during a week are: $Rs. 60, Rs. 65, Rs. 70, Rs. 52.50, Rs. 63, Rs. 73,$ and $Rs. 68$. What is his average daily earning for the week (in $.50$)? (in $Rs.$)