The average marks of a student in four subjects is $75$. If the student obtained $80$ marks in the $5^{th}$ subject,then the new average is?

$A$ club has $15$ men and $25$ women. The average age of men is $10 \text{ years}$ and the average age of women is $12 \text{ years}$. What is the average age of the whole club in years?

The average age of three boys is $15$ years. If the ratio of their ages is $3:5:7$,what is the age of the oldest boy in years?

The average revenue of $13$ consecutive years of a company is $Rs. 70$ lakhs. If the average of the first $7$ years is $Rs. 65$ lakhs and that of the last $7$ years is $Rs. 77$ lakhs,find the revenue for the $7^{th}$ year (in $Rs.$ lakhs).

The sum of three numbers is $98$. If the ratio between the first and second is $2:3$ and between the second and third is $5:8$,then the second number is:

The average weight of $3$ men $A, B$ and $C$ is $84 \, kg$. Another man $D$ joins the group and the average now becomes $80 \, kg$. If another man $E$,whose weight is $3 \, kg$ more than that of $D$,replaces $A$,then the average weight of $B, C, D$ and $E$ becomes $79 \, kg$. The weight of $A$ is (in $kg$)