A car owner buys petrol at $Rs.\,7.50, Rs.\, 8$ and $Rs.\, 8.50$ per $litre$ for three successive years. What approximately is the average cost per litre of petrol if he spends $Rs.\, 4000$ each year ?(in $Rs.$ )
$7.98$
$8$
$8.50$
$9$
The average salary, per head, of all the workers of an institution is $Rs.\, 60 .$ The average salary of $12$ officers is $Rs.\, 400$; the average salary, per head, of the rest is $Rs.\,56.$ The total number of workers in the institution is
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 (in $kg$) of the teacher.
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
The average age of board of directors of a company, having $10$ directors was $48$ years. Coincidentally when a director aged $53$ resigned from the board of directors, another director died on the same day. So a new director joined the board of directors aged $34.$ Next year in the same month the average age of all the $9$ directors was found to be $46 \,years.$ The age of the late (i.e., dead) director at the time of his death was (in $years$)
A batsman makes a score of $270$ runs in the $87^{th}$ inning and thus increases his average by a certain number of runs that is a whole number. Find the possible values of the new average.