$10$ years ago,the average age of a family of $4$ members was $24$ years. Two children have been born (with an age difference of $2$ years),and the present average age of the family remains the same. The present age of the youngest child is (in years):

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 of three numbers is $135$. The largest number is $195$ and the difference between the other two is $20$. The smallest number is:

$A, B, C$ and $D$ are four consecutive odd numbers and their average is $42$. What is the product of $B$ and $D$?

The average age of a husband and wife,who were married $7 \, \text{years}$ ago,was $25 \, \text{years}$ at the time of their marriage. Now,the average age of the family,including the husband,wife,and a child born during the interval,is $22 \, \text{years}$. What is the present age of the child in $\text{years}$?

Out of nine persons,eight persons spent $Rs. \,30$ each for their meals. The ninth person spent $Rs. \,20$ more than the average expenditure of all the nine persons. What was the total money spent by all of them (in $Rs.$)?