The average weight of $21$ boys was recorded as $64 \, kg$. If the weight of the teacher was added,the average increased by $1 \, kg$. What was the teacher's weight (in $, kg$)?

The average monthly income of $P$ and $Q$ is $Rs. 5050$. The average monthly income of $Q$ and $R$ is $Rs. 6250$ and the average monthly income of $P$ and $R$ is $Rs. 5200$. The monthly income of $P$ is

Of the three numbers,the average of the first and the second is greater than the average of the second and the third by $15$. What is the difference between the first and the third of the three numbers?

The total marks obtained by a student in Physics,Chemistry and Mathematics together is $120$ more than the marks obtained by him in Chemistry. What is the average marks obtained by him in Physics and Mathematics together?

$A$ 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?

The average monthly expenditure of a family for the first four months is $Rs. 2750$,for the next three months is $Rs. 2940$,and for the last five months is $Rs. 3130$. If the family saves $Rs. 5330$ throughout the year,find the average monthly income of the family for that year (in $Rs.$).