The average of three numbers is $28$. If the first number is half of the second and the third number is twice the second,then the third number is?

The average age of $8$ men is increased by $2$ years when $2$ of them,whose ages are $20$ years and $24$ years respectively,are replaced by $2$ women. What is the average age of these two women (in years)?

The average height of the students of a class of $20$ is $105 \, cm$. If ten more students of average height of $120 \, cm$ join this class,the average height of the class will become (in $cm$)?

The average age of students of a class is $15.8 \, \text{years}$. The average age of boys in the class is $16.4 \, \text{years}$ and that of the girls is $15.4 \, \text{years}$. The ratio of the number of boys to the number of girls in the class is:

The average age of $5$ sisters is $20 \, \text{years}$. If the age of the youngest sister is $4 \, \text{years}$,what was the average age of the group of sisters at the time of the birth of the youngest sister?

The average age of $20$ boys in the class is $15.6$ years. Five new boys join and the new average becomes $15.56$ years. What is the average age of the five new boys (in years)?