$A$ cricketer,whose bowling average was $12.4$ runs/wicket,takes $5$ wickets for $22$ runs in a match,thereby decreasing his average by $0.4$. The number of wickets taken by him before this match was:

An aeroplane travels $2500 \, km$,$1200 \, km$,and $500 \, km$ at $500 \, km/h$,$400 \, km/h$,and $250 \, km/h$ respectively. The average speed is (in $km/h$):

In an entrance examination,Ritu scored $56$ percent marks,Smita scored $92$ percent marks,and Rina scored $634$ marks. The maximum marks of the examination is $875$. What is the average marks scored by all the three girls together?

The average marks of a group of $20$ students on a test is reduced by $4$ when the topper who scored $90$ marks is replaced by a new student. Find the marks of the new student.

The average age of Donald,his wife,and their two children is $23 \text{ years}$. His wife is $4 \text{ years}$ younger than Donald,and his wife was $24 \text{ years}$ old when his daughter was born. He was $32 \text{ years}$ old when his son was born. What is the average age of Donald and his daughter? (in $\text{years}$)

The average price per $kg$ of rice at $10$ different places was $Rs. 4.85$. After a week,the price per $kg$ was increased by $20$ paise at $3$ places and decreased by $10$ paise at $1$ place. What is the new average price per $kg$ in $Rs.$?