Login/Sign Up
Home » The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular ends are 18 cm and 6 cm. Find the surface area of the frustum.
The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular ends are 18 cm and 6 cm. Find the surface area of the frustum.
CBSE | Class 10 | Exercise 13.4 | Maths | NCERT | Surface Areas And Volumes
The slant height of a frustum of a cone is 4 cm and the perimeters (circumference) of its circular ends are 18 cm and 6 cm. Find the surface area of the frustum.

Given,

Inclination tallness (l) = 4 cm

Perimeter of upper roundabout finish of the frustum = 18 cm

    \[\therefore 2\pi r_1\text{ }=\text{ }18\]

Or on the other hand, r_1 = 9/π

Likewise, periphery of lower end of the frustum = 6 cm

    \[\therefore 2\pi r_2\text{ }=\text{ }6\]

Or on the other hand

    \[,\text{ }r_2\text{ }=\text{ }6/\pi \]

 

Presently, CSA of frustum

    \[=\text{ }\pi \left( r_1+r_2 \right)\text{ }\times \text{ }l\]

    \[=\text{ }\pi \left( 9/\pi +6/\pi \right)\text{ }\times \text{ }4\]

=\text{ }12\times 4\text{ }=\text{ }48\text{ }cm^2

i

More Material