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再次...趕交功課

[匿名]

2007-04-15 4:16 am

as shown in the following figure , a semicircular paper of radius 42 cm is folded so as to form a cone.
a)find the radius of the cone
b)find the volume and the curved surface area of the cone(take pie=3.14 and correct answer to the nearest integer)
c)lf water is filled to a depth of 2/3h,find the wet surface area
d)fine the volume of the water need to fill up the cone (corr.answer to the nearest integer)

回答 (1)

bfaifaiwong

2007-04-15 5:31 am

✔ 最佳答案

a) radius
= (42*2*π/2)/(2π)
= 21cm

b) volume
= (1/3)π(21)²(√(42² - 21²))
= 16789cm³ (corr. to the nearest integer)

curved surface area
= π(21)(42)
= 2769cm² (corr. to the nearest integer)

c) don't know, picture not given + don't know h
But if the cone is putted like V shape and the H is height of the cone
wet surface area
= π(21*2/3)(42*2/3)
= 1231cm² (corr. to the nearest integer)

d) If it ask the volume to fill up the whole cone, the answer is the same as the ans of volume in b?
But if it ask the volume to fill the remain of the cone after water is filled to a depth of 2/3h
= (volume answer in b)*(1 - (2/3)³)
= (volume answer in b)*(19/27)
=11815cm³ (corr. to the nearest integer)

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