If the perimeter of a semi-circular protractor is 36 cm. Find its diameter.
Let r be the radius of the protractor, then
Perimeter = πr + 2r
According to the question,
36 = πr + 2r
⇒ 36 = r(22/7 + 2)
⇒ r = 7 cm.
∴ The diameter of the protractor is (2 × 7) cm = 14 cm.