Question

The circumference of a circle is 88 cm. Its diameter is
(a) 28 cm
(b) 42 cm
(c) 56 cm
(d) none of these

Answer 1

(a) 28 cm
$$\begin{gathered} \mathrm{Circumference}\mathrm{of}\mathrm{the}\mathrm{circle}\mathrm{is}88\mathrm{cm}. \\ \mathrm{Let}\mathrm{the}\mathrm{radius}\mathrm{be}r\mathrm{cm}. \\ \mathrm{It}\mathrm{is}\mathrm{given}\mathrm{that}\mathrm{the}\mathrm{circumference}\mathrm{of}\mathrm{the}\mathrm{circle}\mathrm{is}\left(2\mathrm{\pi r}\right)\mathrm{cm}. \\ \Rightarrow 2\pi r=88 \\ \Rightarrow 2\times \frac{22}{7}\times r=88 \\ \Rightarrow r=\frac{1}{2}\times \frac{7}{22}\times 88 \\ \Rightarrow r=14 \\ \therefore \mathrm{Radius}=14\mathrm{cm} \\ \mathrm{Diameter}=(2\times \mathrm{Radius})=(2\times 14)\mathrm{cm}=28\mathrm{cm} \end{gathered}$$