How does hormone affect a boy's bdy between the age of 11-16 years?

The height of a tree varies as the square root of its age (between 5 to 17 years). When the age of the tree is 9 years, its height is 4 feet. What will be the height of the tree at the age of 16 years?

In a class, there are 40 boys and their average age is 16 years. One boy, ages 17 years, leaving the class and another joining, the average age becomes 15.875 years. The age of the new boys is :

A boy's age is now one third of his mother's age. If mother's present age x years then what is the age of boy after 12 years?

There were 20 boys in a class. The average age increase by 2 months, as a new boy comes in a place of a boy aged 18 years. The age of new boy is?

If a 12 years old boy is replaced by a new boy, then the average age of 18 boys increases by 1.5 years. What is the age of the new boy?

The average age of 30 boys in a class is 15 years. One boy, aged 20 years, left the class, but two new boys came in this place whose age differ by 5 years. If the average age of all boys now in the class becomes 15 years, the age of the younger newcomer is :