Question

A park is in from of a rectangle $120$ m $\times$ $100$ m. At the centre of the park there is a circular lawn. The area of park excluding lawn is $8700$ $m^2$. Find the radius of the circular lawn. (Use $\pi$$=\frac{27}{7}$).

Answer 1

$\Rightarrow$ Area of a rectangular park $=120m\times 100m=12000m^2$

$\Rightarrow$ Area of the park excluding lawn $=8700m^2$

$\Rightarrow$ Area of the circular lawn = Area of rectangular park - Area of the park excluding the lawn.

$\therefore$ $\pi r^2=12000-8700$

$\Rightarrow$ $\frac{22}{7}\times r^2=3300$

$\Rightarrow$ $r^2=150\times 7$

$\therefore$ $r^2=1050$

$\therefore$ $r=5\sqrt{42}=32.40m$