The average age of $5$ sisters is $20 \,year.$ If the age of the youngest sister be $4 \,year,$ what was the average age of the group of sisters at the birth of the youngest sister in $year$ ?

What is the average of all numbers between $8$ and $74$ which are divisible by $7\, ?$

The average age of a group of $15$ students is $10 \,years.$ When $5$ more students joined the group, the average got increased by $1\, year.$ The age of the new student is (in $years$)

The average marks of $120$ students are $35.$ If average of passed students was $39$ and failed students was $15,$ then Find the number of students who have passed?

$5$ 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 batting average for $40$ innings of a cricket player is $50$ runs. His highest score exceeds his lowest score by $172$ runs. If these two innings are excluded. the average of the remaining $38$ innings is $48$ runs. The highest score of the player is