The average marks of Sameer decreased by $1,$ when he replaced the subject in which he scored $40$ marks with two other subjects in which he scored $23$ and $25$ marks respectively. Later,he also included $57$ marks of Computer Science,and the average marks increased by $2.$ How many subjects were there initially?

The mean of the marks obtained by $100$ students is $60$. If the marks obtained by one of the students was incorrectly calculated as $75$ whereas the actual marks obtained by him were $65$,what is the correct mean of the marks obtained by the students?

$A$ batsman makes a score of $81$ runs in the $16^{\text{th}}$ match and thus increases his average runs per match by $3$. What is his average after the $16^{\text{th}}$ match?

Refer to the line graph and answer the given question.
Number of candidates who qualified in a given competitive examination from $6$ states during two given years.
What is the average number of candidates who qualified in the given competitive exam from states $Q, S, T$ and $U$ in $2004$?

The average speed of a train in the onward journey is $25\%$ less than that of the return journey. The train halts for one hour on reaching the destination. The total time taken for the complete to and fro journey is $17\, \text{hours}$,covering a distance of $800\, \text{km}$ (one way). The speed of the train in the onward journey is (in $\text{km/h}$):

The average weight of $36$ students is $50 \,kg$. It was found later that the figure of $37 \,kg$ was misread as $73 \,kg$. What is the correct average? (in $kg$)