Explanation
The area a circle can be expressed in two forms;
[tex]\begin{gathered} \text{Area}=\pi r^2 \\ \text{Area}=\pi(\frac{d}{2})^2 \\ \end{gathered}[/tex]
Where r and d are the radius and the diameter of the circle.
Therefore;
For number 1, r =21 yards,
[tex]\text{Area}=\pi\times21^2=1385.4\text{square yards}[/tex]
Answer: 1385.4 square yards
For number 2, d= 0.4 km
[tex]\text{Area}=\pi\times(\frac{0.4}{2})^2=\pi\times0.2^2=0.1km^2[/tex]
Answer:0.1 square kilometres
