The average age of a class of $30$ students and a teacher reduces by $0.5 \, \text{years}$ if we exclude the teacher. If the initial average is $14 \, \text{years}$,find the age of the class teacher in $\text{years}$.

The average marks of $40$ students in an English exam is $72$. Later,it is found that three marks $64, 62,$ and $84$ were wrongly entered as $68, 65,$ and $73$. The average after the mistakes were rectified is:

$12 \%$ 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 $Rs.\, 1.08$ lakhs,what is Kaushal's monthly salary in $Rs.$?

The average earning of a mechanic for the first four days of a week is $Rs. 18$ and for the last four days is $Rs. 22$. If he earns $Rs. 20$ on the fourth day,his average earning for the whole week is (in $Rs.$)

The average of odd numbers up to $100$ is?

The average price of $80$ computers in an electronic shop is $Rs. 30,000$. If the highest and lowest price computers are sold out,then the average price of the remaining $78$ computers is $Rs. 29,500$. The cost of the highest price computer is $Rs. 80,000$. The cost of the lowest price computer is (in $Rs.$): (in $,000$)