The frustum of a right circular cone has the diameter of a base 10 cm, of top…
2019
The frustum of a right circular cone has the diameter of a base 10 cm, of top 6 cm and a height of 5 cm. Find the slant height of the frustum:
- A.
√29
- B.
4√3
- C.
3√3
- D.
√13
Attempted by 10 students.
Show answer & explanation
Correct answer: A
Solution:
Step-by-step reasoning to find the slant height of the frustum.
Find the radii from the given diameters: radius of the base = 10/2 = 5 cm; radius of the top = 6/2 = 3 cm.
The horizontal leg of the right triangle (along the sloping side) is the difference of the radii: 5 − 3 = 2 cm.
The vertical leg is the height of the frustum: 5 cm.
Apply the Pythagorean theorem to these two legs to get the slant height l:
l = √[(difference of radii)^2 + (height)^2] = √(2^2 + 5^2) = √(4 + 25) = √29.
Therefore the slant height of the frustum is √29 cm (approximately 5.385 cm).
A video solution is available for this question — log in and enroll to watch it.