The average marks of a student in four subjects is $75 .$ If the student obtained $80$ marks in the $5^{\text {th }}$ subject then the new average is?

Average of $a, b$ and $c$ is $11 ;$ average of $c, d$ and $e$ is $17 ;$ average of $e$ and $f$ is $22$ and average of $e$ and $c$ is $17 .$ Find out the average of $a, b,$ $c , d , e$ and $f ?$

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 

In an examination the average marks was found to be $60.$ The marks of $80$ candidates had to be changed from $95$ to $70$ each and the average came down to $55$ marks. The total number of candidates attended the examination were

The average of three numbers is $135 .$ The largest number is $195$ and the diference between the other two is $20 .$ The smallest number is

The average of $11$ numbers is $10.9$ If the average of the first six is $10.5$ and the average of last six is $11.4,$ find the middle (sixth) number.