kanam asked in 科學及數學數學 · 1 decade ago

F.3 Maths

An inverted frustum with a depth of 7 cm. The radii of the top and bottom are 4 cm and 3 cm respectively.

a) Find,in terms of Π, the volume of the frustum.

b) If the frustum is filling with water at a speed of 15 cm3 per second, how much time is required to fill the frustum?

個ans係 a) (259Π/3) cm3

b) 19 s

詳細steps plz..

1 Answer

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  • 1 decade ago
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    The height of the removed portion of the cone = h cm

     h : (h+7) = 3 : 4

     h = 21

    The height of the complete cone = 21 + 7 = 28 cm

    (a)

    Volume of frustum

    = ⅓π(4)²(28) - ⅓π(3)²(21)

    = 259π/3 cm3

    (b)

    Time required

    = (259π/3) / 15

    ≈ 18.1 seconds

    2007-03-11 22:35:22 補充:

    For (b), if it is to be rounded up to the next complete second, then it is 19 seconds.

    2007-03-11 22:35:32 補充:

    For (b), if it is to be rounded-up to the next complete second, then it is 19 seconds.

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