$A$ batsman scores $98$ runs in the $17^{\text{th}}$ match of his career. His average runs per match increases by $2.5$. What is his average before the $17^{\text{th}}$ match?

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 weight of $5$ persons,sitting in a boat,is $38 \, kg$. If the average weight of the boat and the persons sitting in the boat is $52 \, kg$,what is the weight of the boat? (in $kg$)

The average marks of $40$ students in an English exam is $72$. Later,it is found that three marks $64, 62,$ and $84$ were wrongly entered as $68, 65,$ and $73$. The average after the mistakes were rectified is:

$A$ student was asked to find the arithmetic mean of the numbers $3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14$ and $x$. He found the mean to be $12$. What should be the number in place of $x$?

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 $km/h$):