Question

if slant height of the frustum of a cone is 5 cm. if the difference between the radii of it's two circular ends is 4 cm, find the height of the frustum. ​

Answer 1

Let r and R be the radii of the circular ends of the frustum of the cone and h be the height of the frustum.

R-r = 4 and l = 5 cm 

l² = (R-h)² + h²

5² = 4² + h²

h² = 25 - 16 

h² = 9 

h= 3 

Hence , height of the frustum is 3 cm.

Answer 2

l = 5

R - r = 4

h =?

l^2 = h^2 + (R^2 - r^2)

5x5 = h^2 + 4 x 4

25 = h^2 + 16

25 - 16 = h^2

√9 = h

3 = h