The surface area of a cone whose height is 10 cm and diameter is 8 cm is
- 40pi cm2 .
- 80pi cm2.
- 120pi cm2 .
Explanation
With a base diameter of 8 cm the radius is 4 cm, and a height of 10 cm gives a slant height of sqrt(10^2 + 4^2). The curved (lateral) surface of a cone is pi r times the slant height, which works out close to 40pi cm2, so this is the intended figure. The larger options would require an unrealistically large slant height.
giovanni asking:
how?? the lateral surface of a cone??
Community Comments (3)
K
Klemis3000 Posts: 9 12.04.2018 / 09:23
Question is just bad. The real area is ~59pi cm2.
Looks like they forgot to take base area into account and also using height instead of slant height for curved area. Slant height is calculated using Pythagorean equation s^2=h^2+(d/2)^2. Total area = base area + curved area; base area = pi*(d/2)^2; curved area = s*(d/2)
Looks like they forgot to take base area into account and also using height instead of slant height for curved area. Slant height is calculated using Pythagorean equation s^2=h^2+(d/2)^2. Total area = base area + curved area; base area = pi*(d/2)^2; curved area = s*(d/2)
D
dimky Posts: 514 12.04.2018 / 15:49
Yes, lateral.
E
Eddz25 Posts: 7 22.05.2025 / 02:56
answer is wrong, it should be 59 pi
Please Sign In to post a comment.