Question

The radii of end of a frustum are 14cmand 7cm respectively, it's slant height is 21 cm .Find curved surface area

Answer 1

Given:-

• The radii of ends of a frustum are 14cm and 7cm.
• Slant height of frustum is 21cm.

To find:-

• Find the curved surface area of the frustum.?

Solutions:-

• Let the radius of one end of frustum be 'R' and radius of another end be 'r'.

We know that,

Curved surface area of the frustum = π(R + r)

=> 22/7 × 21 (14 + 7)

=> 22 × 3 × 21

=> 66 × 21

=> 1386cm²

Hence, the CSA of the frustum is 1386cm².

Some Important:-

Curved Surface Area and Total Surface Area of the Frustum

• The curved surface area of the frustum of the cone = π(R+r)l1

• The total surface area of the frustum of the cone = π l1 (R+r) +πR2 +πr2

• The slant height (l1) in both the cases shall be = √[H2 +(R-r)2]