Three years ago,the average age of a family of $5$ members was $27 \, \text{years}$. The present average age is also $27 \, \text{years}$ after the inclusion of a child into the family. Find the age of the child in years.

The average age of $5$ boys is $16$ years, of which the average age of $4$ boys is $16$ years $3$ months. The age of the $5^{th}$ boy is:

Ashish has earned an average of $4200$ dollars for the first eleven months of the year. If he justifies his staying on in the $US$ on the basis of his ability to earn at least $5000$ dollars per month for the entire year,how much should he earn (in dollars) in the last month to achieve his required average for the whole year?

The average of three consecutive odd numbers is $52$ more than $\frac{1}{3}$ of the largest of these numbers. What is the smallest of these numbers?

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.

$A$ batsman scores $87$ runs in the $21^{st}$ match of his career. His average runs per match increase by $2.$ What is his average before the $21^{st}$ match?