Question

A circle having 21 cm radius is cut into 3 equal parts to make 3 equal circular cones. Then what will be the radius of such cone ?

Answer 1

Radius of the circle = 21 cm 

Then the circumference of circle 

= 2πr = 2 × \(\frac{22}{7}\) × 21 = 132 cm 

\(\frac{1}{3}\)of this circumference of circle = 

Circumference of the ground of the cone 

= \(\frac{1}{3}\) × 132 = 44 cm

 Now let the ground radius of new cone = r

Then its ground circumference = 2πr = 44

So ground radius of cone = 7 cm.