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[匿名]

2010-04-08 6:56 am

圖片參考：http://imgcld.yimg.com/8/n/HA00510450/o/701004070207713873381390.jpg

In the figure, a similar but smaller pyramid is cut from a larger one to form a frustum. The 2 bases of the frustum are squares with sides of 8 cm and 10 cm respectively. The height of the original pyramid is 24 cm.

Find the total surface area of the frustum formed. Answer:344cm^2

更新1:

答案是344cm²(可能是準確至3位有效數字)

回答 (2)

用戶2053

2010-04-08 9:02 am

✔ 最佳答案

The height of the Front or Right face △ = √(24^2 + 10^2) = 26 cm
The total surface (not include the base)of the original pyramid
= Front face + Right face + Back face + Left face
= 10*26/2 + 10*26/2 + 10*24/2 + 10/24/2
= 260 + 240 = 500 cm^2
The surface area ( not include the base) of
(smaller pyramid : original pyramid) = (8 : 10)^2
smaller pyramid : 500 = 16 : 25
smaller pyramid = 320cm^2
So the total surface area of the frustum (not include the top and the base)
= 500 - 320 = 180cm^2
Hence the total surface area of the frustum = 180 + 8^2 + 10^2
= 344 cm^2

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用戶7639

2010-04-08 7:19 am

340cm²??????

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