The average speed of a train running at a speed of $30 \, km/h$ during the first $100 \, km$,at $40 \, km/h$ during the second $100 \, km$,and at $50 \, km/h$ during the last $100 \, km$ is nearly (in $km/h$):

What is the average of all numbers between $100$ and $200$ which are divisible by $13$ (in $.5$)?

The average of $17$ numbers is $10.9$. If the average of the first $9$ numbers is $10.5$ and the average of the last $9$ numbers is $11.4$, find the middle number.

In an examination,the average marks obtained by the girls of a class is $85$ and the average marks obtained by the boys of the same class is $87$. If the girls and boys are in the ratio $4:5$,the average marks of the whole class (approx.) is closest to:

Of the three numbers whose average is $60$,the first is one-fourth of the sum of the others. The first number is

The average age of a cricket team reduces by $2$ when two senior players aged $32$ and $30$ are replaced by $2$ youngsters of equal age. What is the age of these youngsters?