The mean weight of $34$ students of a school is $42 \, kg$. If the weight of the teacher is included,the mean weight increases by $400 \, g$. Find the weight of the teacher (in $kg$).

The average of $12$ results is $15,$ and the average of the first two is $14.$ What is the average of the rest?

If the mean of $5$ observations $x, x+2, x+4, x+6$ and $x+8$ is $11,$ then the mean of the last three observations is

$A$ man spends $Rs. 1800$ monthly on an average for the first four months and $Rs. 2000$ monthly for the next eight months and saves $Rs. 5600$ a year. His average monthly income is (in $Rs.$)

Of the three numbers,the second is twice the first and is also thrice the third. If the average of the three numbers is $44,$ the largest number is

Three $years$ ago,the average age of a family of $5$ members was $17$ $years$. With the birth of a new baby,the average age of the family remains the same even today. Find the age of the baby (in $years$).