The average marks of $120$ students are $35.$ If the average of passed students was $39$ and failed students was $15,$ then find the number of students who have passed.

Out of seven given numbers,the average of the first four numbers is $4$ and that of the last four numbers is also $4$. If the average of all the seven numbers is $3,$ then the fourth number is?

Of the three numbers,the first is twice the second and the second is twice the third. The average of the reciprocals of the numbers is $\frac{7}{72}$. The numbers are:

In a class,the average height of $35$ girls was measured as $160 \,cm$. Later,it was discovered that the height of one of the girls was misread as $144 \,cm$,while her actual height was $104 \,cm$. What was the actual average height of the girls in the class? (in $cm$) (rounded off to two digits after decimal)

If the mean of $a, b, c$ is $M$ and $ab + bc + ca = 0$,then the mean of $a^2, b^2, c^2$ is

Out of nine persons,eight persons spent $Rs. \,30$ each for their meals. The ninth person spent $Rs. \,20$ more than the average expenditure of all the nine persons. What was the total money spent by all of them (in $Rs.$)?