The average weight of $36$ students is $50 \,kg$. If was found later that the weight of one of the student was misread as $73 \,kg$. whereas his actual weight was $37 \,kg$. Find the correct average. (in $kg$)

A club has $15$ men and $25$ women. The average age of men is $10\, years$ and the average age of women is $12 \,year.$ What is the average age of the whole club in $year$?

The average age of $11$ players of a cricket team is increased by $2 \,months$ when two of them aged $18\, years$ and $20 \,years$ are replaced by two new players. The average age of the new players is?

The arithmetic mean of $100$ observations is $24.6$ is added to each of the observations and, then each of them is multiplied by $2.5 .$ Find the new arithmetic mean.

The average age of Sachin and Ganguli is $35 \,years.$ If Kaif replaces Sachin, the average age becomes $32 \,years$ and if Kaif replaces Ganguli, then the average age becomes $38 \,years.$ If the average age of Dhoni and Irfan be half of the average age of Sachin, Ganguli and Kaif, then the average age of all the five people is:

The average of first three numbers is double of the fourth number. If the average of all the four numbers is $12,$ find the $4^{th}$ number.