Question

A park is in the form of a rectangle $120m\times 100m$. At the centre of the park there is a circular lawn. The area of park excluding lawn is $8700m^2$. Find the radius of the circular lawn. (Use $\pi =\frac{22}{7}$)

Answer 1

Area of the park $=(120\times 100)m^2=12000m^2$

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

$\therefore$ Area of the circular lawn $=(12000-8700)m^2$

$\Rightarrow \pi r^2=3300$

$\Rightarrow r^2=3300\times \frac{7}{22}=150\times 7$

$\Rightarrow r=\sqrt{150\times 7}=32.40m$