It rained as much on Wednesday as on all the other days of the week combined. If the average rainfall for the whole week was $3 \, cm$,then how much did it rain on Wednesday? (in $cm$)

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.

The sum of three consecutive odd numbers is $38$ more than the average of these numbers. What is the first of these numbers?

The average age of a family of $6$ members $4$ years ago was $25$ years. Meanwhile,a child was born in this family,and the average age of the whole family is still the same today. The present age of the child in years is?

The average salary of the entire staff in an office is $Rs. 120$ per month. The average salary of officers is $Rs. 460$ and that of non-officers is $Rs. 110$. If the number of officers is $15$,then find the number of non-officers in the office?

The average of the first $n$ consecutive even numbers is $101$. Find their sum.