A circular ground whose diameter is 30 metres has a 1.5 m broad garden around it. What is the area of the garden in square metres?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 148.5 m2
The garden is a ring between the edge of the ground and a circle 1.5 m further out, so its area is the area of the outer circle minus the area of the ground.
Radius of the ground \(r=30\div2=15\,\mathrm{m}\)
Outer radius \(R=15+1.5=16.5\,\mathrm{m}\)
Area \(=\pi(R^2-r^2)=\pi(16.5+15)(16.5-15)=\pi\times31.5\times1.5\)
\(\displaystyle=\frac{22}{7}\times47.25=148.5\,\mathrm{m}^2\)