The average of $6$ numbers is $8$. What is the $7^{th}$ number so that the average becomes $10$?

The average marks of a group of $20$ students on a test is reduced by $4$ when the topper who scored $90$ marks is replaced by a new student. Find the marks of the new student.

The average age of $5$ boys is $16$ years, of which the average age of $4$ boys is $16$ years $3$ months. The age of the $5^{th}$ boy is:

The average monthly salary of $20$ employees in an organisation is $Rs. 1500$. If the manager's salary is added, then the average salary increases by $Rs. 100$. What is the manager's monthly salary (in $Rs.$)?

In a $20$ over match,the required run rate to win is $7.2$. If the run rate is $6$ at the end of the $15^{th}$ over,the required run rate to win the match is

The average of three numbers is $154$. The first number is twice the second and the second number is twice the third. The first number is