In a match,the average of runs scored by five players is $49$. If the runs scored by four players are $75, 30, 63,$ and $21$ respectively,then how many runs did the fifth player score?

$A, B, C$ and $D$ are four consecutive even numbers,respectively,and their average is $65$. What is the product of $A$ and $D$?

Out of three numbers,the first is twice the second and is half of the third. If the average of the three numbers is $56$,the three numbers in order are

The average weight of a group of $20$ boys was calculated to be $89.4 \, kg$ and it was later discovered that one weight was misread as $78 \, kg$ instead of $87 \, kg$. The correct average weight is (in $kg$).

The arithmetic mean of the following numbers is $1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7$.

$A$ car owner buys petrol at $Rs. 7.50$,$Rs. 8$,and $Rs. 8.50$ per litre for three successive years. What is the approximate average cost per litre of petrol if he spends $Rs. 4000$ each year?