Question

If the perimeter of a semicircular protractor is 54cm,then its diameter (in cms) is..........

Answer 1

Perimeter of a semi circle = πr
Given, its perimeter = 54 cm.
So, πr = 54 ⇒ r = 54 / 3.14 = 17.197 cm (approx)

Diameter = 2r = 17.197 x 2 = 34.394 cm (approx)

Answer 2

The perimeter simply means the distance round a figure, in a semicircular protractor the distance round this figure is inclusive of the circumference of the semi circular part plus the diameter of the protractor. the formula of finding the circumference is $\pi$ multiply by a half added to the diameter which sums up to 54.