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 $years$)

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

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 of $30$ numbers is $15 .$ The average of the first $18$ numbers is $10$ and that of the next $11$ numbers is $20 .$ The last number is

A cricketer had a certain average of runs for his $64$ innings. In his $65^{th}$ innings, he is bowled out for no score on his part. This brings down his average by $2$ runs. His new average of runs is?

The average weight of five persons sitting in a boat is $38\, kg.$ The average weight of the boat and the persons sitting in the boat is $52\, kg.$ What is the weight of the boat (in $kg$)?