There was one mess for $30$ boarders in a certain hostel. On the number of boarders being increased by $10,$ the expenses of the mess were increased by $Rs.\,40$ per month while the average expenditure per head diminished by $Rs.\,2.$ Find out actual monthly expenses. (in $Rs.$)

The average of two numbers $A$ and $B$ is $20 ,$ that of $B$ and $C$ is $19$ and of $C$ and $A$ it is $21 .$ What is the value of $A ?$

$12 \%$ of Kaushal's monthly salary is equal to $16 \%$ of Nandini's monthly salary. Suresh's monthly salary is half that of Nandini's monthly salary. If Suresh's annual salary is $Rs.\,1.08$ $lacs.$ What is Kaushal's monthly salary? (in $Rs.$)

A class has $20$ boys and $30$ girls. The average age of boys is $11\, years $ and that of girls is $12\,years.$ What is the average age of the whole class in $year$

The average weight of $24$ students is $35\, kgs.$ If the weight of teacher is added the average increased by $400\, gms$. What is the weight of the teacher? (in $kg$)

The average marks obtained by $40$ students of a class is $86 .$ If the $5$ highest marks are removed, the average reduces by one mark. The average marks of the top $5$ students is