The average monthly income of $P$ and $Q$ is $Rs. 5050$. The average monthly income of $Q$ and $R$ is $Rs. 6250$ and the average monthly income of $P$ and $R$ is $Rs. 5200$. The monthly income of $P$ is

The average weight of $10$ students is increased by $0.5 \, kg$ when one of the students weighing $50 \, kg$ is replaced by a new student. Find the weight of the new student (in $kg$).

The average of the two-digit numbers,which remain the same when the digits interchange their position,is:

The average marks obtained by $180$ students in an examination is $50$. If the average marks of passed students is $80$ and the average marks of failed students is $40$,then what is the number of students who failed the examination?

Nine friends have a dinner in a hotel. Eight of them spent $Rs. 12$ each on their meals and the ninth spent $Rs. 16$ more than the average expenditure of all the nine. Find out the total money in $Rs.$ spent by them?

In a class,there are $20$ boys whose average age is decreased by $2$ months,when one boy aged $18$ years is replaced by a new boy. The age of the new boy is: