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

The average age of a graph of $9$ students is $20\, years.$ When $6$ more students joined the group, the average age falls by $2\, years.$ Then the average age of new students is

David obtained $76,65,82,67$ and $85 \,marks$ (out of $100$ ) in English, Mathematics, Physics, Chemistry and Biology. What is his average $marks$ ?

$5$ members of a team are weighed consecutively and their average weight calculated after each member is weighed. If the average weight increases by one kg each time, how much heavier is the last player than the first one? (in $kg$)

The average age of $35$ students in a class is $16\, years.$ The average age of $21$ students is $14$ What is the average age of remaining $14$ students ?(in $years$)

In a $20$ over match, the required run rate to win is $7.2 .$ If the run rate is $6$ at the end of the $15^{th}$ over, the required run rate to win the match is