Question

If the perimeter of semicircular protractor is 108cm ,then find the diameter of the protractor.

Answer 1

Hi ,

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

I hope this helps you.

:)

Answer 2

Hope it helps...

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