The mean marks of $10$ boys in a class is $70 \%$, whereas the mean marks of $15$ girls is $60 \%$. The mean marks of all the $25$ students is
$64$
$60$
$55$
$52$
The average of $6$ observations is $12 .$ A new seventh observation is included and the new average is decreased by $1$. The seventh observation is
Out of four numbers, whose average is $60,$ the first one is one-fourth of the sum of the last three. The first number is
The average of $12$ results is $15,$ and the average of the first two is $14.$ What is the average of the rest?
The average score of Rahul, Manish and Suresh is $63.$ Rahul's score is $15$ less than Ajay and $10$ more than Manish. If Ajay scored $30$ marks more than the average score of Rahul, Manish and Suresh, what is the sum of Manish's and Suresh's scores ?
The average age of $A, B, C, D$ five years ago was $45\, years.$ By including $x$, the present average age of all the five is $49\, years.$ The present age of $x$ is (in $years$)