In a family, the average age of a father and a mother is $35\, years.$ The average age of the father, mother and their only son is $27\, years.$ What is the age of the son ? (in $years$)
$12$
$11$
$10.5$
$10$
What is the average of first $10$ even numbers ?
The average of nine numbers is $50.$ The average of the first five numbers is $54$ and that of the last three numbers is $52 .$ Then the sixth number is?
The average age of $8$ men is increased by $2\, years.$ When $2$ of them, whose ages are $20\, years$ and $24 \,years$ respectively, are replaced by $2$ women. What is the average age of these two women ? (in $years$)
An aeroplane flies along the four sides of a square field at speeds of $200,400,600$ and $800\, km / hr$. The average speed of the plane in the flight around the field in $km / hr$ is:
In an examination, out of $20$ students in a class, in Mathematics $2$ students scored $100$ marks $, 3$ students scored $0,$ and average marks for rest of the students was $40 .$ What is the average mark of the whole class ? (in $marks$)