The radius of a sector is 21cm and it central angle is 120 . Find the

1.	The radius of a sector is 21cm and it central angle is 120 . Find the perimeter of sector
Answer» consider a full sphere of radius 21 cm. what is the perimeter of that full CIRCLE? it is 2 pi R = 42pi now, we know a full circle has an ANGLE 360 so a sector having angle 120 is (120/360) of a complete circle right? ( I just took the ratio of the angle of sector to the angle of the sphere) 120/360 = 1/3 so sector = 1/3 x full circle therefore perimeter or circumference of the sector = 1/3 x perimeter of circle = 1/3 x 42pi =14pi = 14 x 3.14 = 43.96 =44.0

The radius of a sector is 21cm and it central angle is 120 . Find the perimeter of sector

Answer»

consider a full sphere of radius 21 cm.

what is the perimeter of that full CIRCLE?

it is 2 pi R

= 42pi

now, we know a full circle has an ANGLE 360

so a sector having angle 120 is (120/360) of a complete circle right? ( I just took the ratio of the angle of sector to the angle of the sphere)

120/360 = 1/3

so sector = 1/3 x full circle

therefore perimeter or circumference of the sector = 1/3 x perimeter of circle

= 1/3 x 42pi

=14pi = 14 x 3.14 = 43.96 =44.0