Question

If the perimeter of a semicircular protractor is 108cm find the diameter of the protractor

Answer 1

Let radius of the semicircle = r cm

Perimeter of the

semicircle = 2r + pi × r

= ( 2 + pi )r

= ( 2 + 22/ 7 ) r

= [( 14 + 22 ) / 7 ] r

P = 36r / 7 -----( 1 )

According to the problem given ,

P = 108 cm -----------( 2 )

( 1 ) = ( 2 )

36r/ 7 = 108

r = ( 108 × 7 ) / 36

r = 3 × 7

r = 21 cm

Therefore ,

Diameter of the semicircle = 2r

d = 2 × 21

d = 42 cm