The average age of $30$ girls is $1\, year.$ The average of first $18$ girls is $15\, year.$ Find out the average age of remaining $12$ girls?

The average of the first $7$ integers in series of $13$ consecutive odd integers is $37 .$ What is the average of the entire series ?

The bowling average of a cricketer was $12.4 .$ He improves his bowling average by $0.2$ points, when he takes $5$ wickets for $26$ runs in his last match. The number of wickets taken by him before the last match Was?

The average temperature of Monday, Tuesday, Wednesday and Thursday is $60^{\circ}$. The average temperature for Tuesday, Wednesday, Thursday and Friday is $63^{\circ}$. If the ratio of temperature for Monday and Friday is $21: 25,$ then what is the temperature of Friday? (in $^{\circ}$)

The average of $5$ quantities is $6 .$ The average of three of them is $8 .$ What is the average of remaining two quantities?

The average weight of $A , B$ and $C$ is $45\, kg$. If the average weight of $A$ and $B$ is $40 \,kg$ and that of $B$ and $C$ is $43\, kg$, then the weight of $B$ is