Question

4. A sector of central angle 90° is cut out from a circle of radius 12 centimetres and is rolled a up into a cone. a) What is its slant height ? b) What is its radius ? c) What is its curved surface area ? ​

Answer 1

Answer:

Any circular sheet, when divided into 3 equal parts, central angle of sector is (360°÷3) 120°

Radius of circle becomes slant height of cone, made by rolling sector. So slant height is 12 cm.

Curved surface area of cone remains same to that of area of sector.

CSA=π × 122 × 120°360°

CSA=48π cm2

Answer 2

Answer:

Slant ht= 12cm

CSA = 36πcm2