Question

Find the perimeter of a semicircular protractor whose diameter is 14 cm. [CBSE 2009]

Answer 1

Perimeter of a semicircular protractor = Circumference of semicircular protractor + diameter of semicircular protractor
$$\begin{gathered} =\frac{1}{2}\left(2\mathrm{\pi }r\right)+d \\ =\mathrm{\pi }r+d \\ =\mathrm{\pi }\frac{d}{\mathit{2}}+d \\ =\frac{22}{7}\times 7+14 \\ =22+14 \\ =36\mathrm{cm} \end{gathered}$$
Hence, the perimeter of a semicircular protractor is 36 cm.