The average of $25$ results is $20$. The average of the first $12$ results is $15$ and that of the last $12$ results is $18$. Then,the $13^{th}$ result is:

The average of $50$ numbers is $38$. If two numbers $45$ and $55$ are discarded,the average of the remaining set of numbers is:

The average of the first $46$ natural numbers is:

The average income of $A$ for $15$ days is $Rs. 70$. The average for the first five days is $Rs. 60$ and that for the last nine days is $Rs. 80$. $A$'s income for the sixth day is (in $Rs.$):

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 marks of $40$ students in an English exam is $72$. Later,it is found that three marks $64, 62,$ and $84$ were wrongly entered as $68, 65,$ and $73$. The average after the mistakes were rectified is: