The average of the two-digit numbers,which remain the same when the digits interchange their position,is:

The average marks in English subject of a class of $24$ students is $56$. If the marks of three students were misread as $44, 45$ and $61$ instead of the actual marks $48, 59$ and $67$ respectively,then what would be the correct average?

What is the average of the squares of the first $19$ natural numbers?

The average of $50$ numbers is $38$. If two numbers,namely,$45$ and $55$ are discarded,what is the average of the remaining numbers (in $.5$)?

$10$ years ago,the average age of a family of $4$ members was $24$ years. Two children have been born (with an age difference of $2$ years),and the present average age of the family remains the same. The present age of the youngest child is (in years):

$A$ man travels by a car to his office at $60 \, km/h$ and returns home along the same route at $20 \, km/h$. Find the average speed of his whole journey (in $km/h$).