Maths(area....)MC

amy

2011-02-07 12:34 am

1.The total surface areas of a cube and a sphere and the same.If the radius of the sphere is6cm,find the length of the side of the cube.(answer in square root)
A.24πcm
B.48πcm
C.12πcm
D.16πcm

2.The figure shows a cuboid ABCDEFGH which of the following solids has a volume two times that of pyramid DEFH?

圖片參考：http://imgcld.yimg.com/8/n/HA00772322/o/701102060064513873377620.jpg
A.pyramidCBAG
B.pyramidBCDEH
C.prismABHEFG
D.None of the above

3.If the surface area of a sphere is increased by 300%,then the volume of the sphere will be increased by
A.300%
B.400%
C.700%
D.800%

回答 (1)

myisland8132

2011-02-07 1:39 am

✔ 最佳答案

1 The total surface area of a sphere = 4π(6)^2 = 144π cm^2If the length of the side of the cube is x cm6x^2 = 144πx = sqrt(24π) (A)2 Volume of pyramid DEFH = (EF)(EH)(DE)/6Volume of pyramid BCDEH = (BC)(EH)(DE)/3ANSWER: B3 Let the original and new raduii of a sphere are r and r'Then 4π(r')^2 = 4(4πr^2) = 16πr^2=> r' = 2rSo, the volume of the sphere will be increased by 2^3 - 1 = 700% (C)

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