Answer:
x = 20 , SA = 960π cm²
Step-by-step explanation:
The small cone and the larger cone are similar
The the ratio of corresponding sides are in proportion , that is
[tex]\frac{x}{4}[/tex] = [tex]\frac{35}{7}[/tex] = 5 ( multiply both sides by 4 )
x = 20 cm
The frustum is the part of the cone between the two parallel planes
That is the yellow shaded part in the diagram.
The surface area (SA) is calculated as
SA = πr² + πrl ( r is the radius and l the slant height )
For the frustum , r = 20 and l = 35 - 7 = 28, then
SA = π × 20² + π × 20 × 28
= 400π + 560π
= 960π cm²
