The average of marks obtained by $120$ candidates in a certain examination is $35 .$ If the average marks obtained by passed candidates are $39$ and those of the failed candidates are $15,$ then what is the number of candidates who passed the examination?
$100$
$120$
$150$
$140$
The average of a non-zero number and its square is $5$ times the number. The number is
If the average of $m$ numbers is $n^{2}$ and that of $n$ numbers is $m^{2},$ then the average of $( m + n )$ numbers is
In an examination average marks obtained by the girls of a class is $85$ and the average marks obtained by the boys of the same class is $87 .$ If the girls and boys are in the ratio $4: 5,$ average marks of the whole class $(approx.)$ is closest to
The average of the squares of of first ten natural numbers is
Average weight of $25$ persons is increased by $1 \,kg ,$ when one man weighing $60\, kg$ is replaced by a new person. Weight of new person is? (in $kg$)