Question

If the perimeter of a semicircular protractor is $36cm$, then its diameter is :

• A. $10cm$
• B. $12cm$
• C. $14cm$
• D. $15cm$

Answer 1

Answer: (C)

$14cm$

Perimeter of semicircular protractor$=36$ cm

$\pi r+2r=36\Rightarrow (\pi +2)r=36\Rightarrow (\frac{22}{7}+2)r=36\Rightarrow \frac{36}{7}r=36\Rightarrow r=\frac{36\times 7}{36}\Rightarrow r=7$

Therefore, diameter $=2r=2\times 7=14$ cm