Question

Find the diameter of a circle whose circumference is
(i) 12.56 cm
(ii) 88 m
(iii) 11.0 km

Answer 1

(i) ​We know that the circumference C of a circle of diameter 'd' is given by:
C = $\mathrm{\pi }$d
$$\begin{gathered} \Rightarrow d=\frac{C}{\mathrm{\pi }} \\ \mathrm{Here},C=12.56\mathrm{cm} \\ \Rightarrow d=\frac{12.56\times 7}{22}\mathrm{cm}=\frac{87.92}{22}\mathrm{cm}=3.99\mathrm{cm}. \end{gathered}$$

(ii) ​We know that the circumference C of a circle of diameter 'd' is given by:
C = $\mathrm{\pi }$d
$$\begin{gathered} \Rightarrow d=\frac{C}{\mathrm{\pi }} \\ \mathrm{Here},C=88\mathrm{m} \\ \Rightarrow d=\frac{88\times 7}{22}\mathrm{m}=28\mathrm{m}. \end{gathered}$$

(iii) ​We know that the circumference C of a circle of diameter 'd' is given by:
C = $\mathrm{\pi }$d
$$\begin{gathered} \Rightarrow d=\frac{C}{\mathrm{\pi }} \\ \mathrm{Here},C=11\mathrm{km} \\ \Rightarrow d=\frac{11\times 7}{22}\mathrm{km}=\frac{7}{2}\mathrm{km}=3.5\mathrm{km}. \end{gathered}$$