area and volume

👨🏻‍🏫 學術台數學

[匿名]

2010-12-18 8:49 pm

The figure shows a concial object that is composed of a small right circular cone VAB and a frustum ACDB.The heights of the small circular cone and the frustum are 3m and 4m respectively

a.Find the ratio of the curved surface area of the small curved surface area of the small circular cone to that of the frustum

b.The curved surface of the small circular cone is now painted in purple,and that of the frustum is painted in green. If 2 cans of purple paint have been used to paint the cone,how many cans of green paint are required to paint the frustum?

更新1:

answer a.9:40 b.80/9

更新2:

唔知道步驟

回答 (2)

myisland8132

2010-12-18 10:23 pm

✔ 最佳答案

(a) Add the small right circular cone VAB to a frustum ACDB. Then the big right circular cone VCD has height 3+4=7 cm.

So, the ratio of the curved surface area of the small circular cone to that of the big circular cone is 3^2 : 7^2 = 9 : 49.

Now the curved surface area of frustum ACDB is equal to curved surface area of big circular cone - curved surface area of small circular cone. So the ratio of curved surface area of the small circular cone to that of the frustum is 9 : (49-9) = 9 : 40

(b) 2 : ( cans of green paint for frustum) = 9 : 40
40 * 2 = 9(cans of green paint for frustum)
cans of green paint for frustum = 80/9

👍 0 👎 0

小魚

2010-12-18 9:51 pm

sorry about that...where is your graph

👍 0 👎 0

收錄日期: 2021-04-26 14:02:56
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20101218000051KK00403

檢視 Wayback Machine 備份