$20$ persons went to a hotel for a combined dinner party. $15$of them  spent $₹90$ each on their dinner and rest spent $₹30$ more than the average expenditure of all the $20.$ What was  the total money spent  ( in $₹$ ) by them$?$

The average price of $3$ precious diamond studded platinum thrones is ₹$97610498312$. If their prices are in the ratio $4:7:9$. The price of the cheapest is

The average weight of $23$ boxes is $3$ kg. If the weight of the container (in which the boxes are kept)is included, the calculated average weight per box increase by $1$kg . What is the weight of container. 

A man covers $1/4$th of his journey by cycle in $40km/h$, the $1/2$ of the remaining by car at $20km/h$, and the rest by walking at $10km/h$. Find his average speed during the whole journey.

The average age of a group of $15$ persons is $25$years and $5$ months. Two persons, each $40$ years old, left the group. What will be the average age of the remaining persons in the group?

The  average  salary of the entire staff in an department  is Rs. $2000$ per month . The average salary of officers is Rs. $3000$ and that of non-officers is Rs. $1500$. If the number of officers is $10$, then find the number of non-officers in the office?

The average of $\text{'}n\text{'}$ numbers is$z.$ If the number $x$ is replaced by the number  $x^1$, then the average becomes $z^1$. Find the relation between$n, z,$ $z^1$$, x$ and $x^1$.