The mean weight of $34$ students of a school is $42 \,kg$. If the weight of the teacher be included, the mean rises by $400 \,g$. Find the weight of the teacher (in $kg$).
$55$
$57$
$66$
$56$
The average of first nine prime numbers is
Of the three numbers whose average is $60,$ the first is one-fourth of the sum of the others. The first number is
The average age of $8$ men is increased by $2\, years.$ When $2$ of them, whose ages are $20\, years$ and $24 \,years$ respectively, are replaced by $2$ women. What is the average age of these two women ? (in $years$)
The average weight of a class of $24$ students is $35 \,kg$. If the weight of the teacher is included the average rises by $400\, g.$ The weight of the teacher is (in $kg$)
A number, $x,$ equals $80 \%$ of the average of $5,7,$ $14$ and a number $y$. If the average of $x$ and $y$ is $26$ then value of $y$ is