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 temperature for Monday, Tuesday, Wednesday and Thursday was $48^{\circ}$. The average temperature for Tuesday, Wednesday, Thursday and Friday was $52^{\circ} .$ If the temperature on Monday was $42^{\circ} .$ then the temperature on Friday was (in $degrees$)

The average age of a graph of $9$ students is $20\, years.$ When $6$ more students joined the group, the average age falls by $2\, years.$ Then the average age of new students is

The average speed of a cyclist who covers first, second and third km at $20,16$ and $12\, km / hr$ respectively ( in $km / hr )$ is

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?

A student bought $4$ books for $Rs. \,120$ from one book shop and $6$ books for $Rs.\, 150$ from another. The average price (in rupees), he paid per book was