Question

If the perimeter of a semicircle protractor is 66cm, find the radius of the protractor.​

Answer 1

Explanation:

Perimer of protractor=l+2r....(1)

l=(teta/360)×2× pai×r.....(2)

(in semicircle teta=180°)

Perimeter=(180/360)×2×(22/7)×r+2r

66=(22/7)×r+2r

(66×7/22)=2(r/2 +r)

21=2(r/2+r)

21/2 =r/2+r

(Multiplying both sides by 2)

21=r+2r

3r=21

r=21/3

r=7.

The radius of the protractor is 7 cm.

Answer 2

• Solution:

1/2 Circumstances + Diameter = Perimeter of D

πr + d = 66

(22 / 7 × r) + 2r = 66

r + 2r = 21

3r = 21

r = 21/3

r = 7cm