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Frustums

discia.org 10 questions · 41 marks
Name Date
  1. Either paper 3 marks

    The diagram shows a frustum. It was made by standing a cone on its base and slicing a smaller cone off the top, parallel to the base.

    32 cm15 cm3 cm

    The frustum has base radius \(15\) cm, top radius \(3\) cm and height \(32\) cm.

    Find the height of the cone that was removed.

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    \(8\ \text{cm}\)
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  2. Either paper 4 marks

    A cone of height \(54\) cm and base radius \(18\) cm had a smaller cone sliced off the top, parallel to the base. The solid left behind is the frustum shown.

    18 cm3 cm

    The top of the frustum is a circle of radius \(3\) cm, and the cone that was removed is \(9\) cm tall.

    Volume of a cone \(= \frac{1}{3}\pi r^2 h\)

    Work out the volume of the frustum. Give your answer in terms of \(\pi\).

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    \(5805\pi\ \text{cm}^3\)
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  3. Either paper 5 marks

    A solid cone has base radius \(15\) cm and height \(45\) cm.

    A cone of height \(18\) cm is removed from the top of it, by cutting parallel to the base. The solid left behind is the frustum shown.

    27 cm15 cm

    Volume of a cone \(= \frac{1}{3}\pi r^2 h\)

    (a)

    Calculate the radius of the circular top of the frustum.

    (b)

    Calculate the volume of the frustum. Give your answer in terms of \(\pi\).

    Show answer
    (a) \(6\ \text{cm}\)
    (b) \(3159\pi\ \text{cm}^3\)
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  4. Either paper 4 marks

    Here is a frustum, made by slicing a smaller cone off the top of a cone of slant height \(60\) cm.

    20 cm5 cm45 cm

    The base radius is \(20\) cm and the top radius is \(5\) cm.

    Curved surface area of a cone \(= \pi r l\), where \(l\) is the slant height.

    Work out the curved surface area of the frustum. Give your answer in terms of \(\pi\).

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    \(1125\pi\ \text{cm}^2\)
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  5. Calculator 5 marks

    A vase is the shape of a frustum, made by removing a cone of height \(36\) cm from the top of a cone of height \(60\) cm. It stands on its wider end, and the opening is the smaller circle on top.

    24 cm10 cm6 cm

    The base has radius \(10\) cm, the opening has radius \(6\) cm, and the vase is \(24\) cm deep.

    Volume of a cone \(= \frac{1}{3}\pi r^2 h\)

    Work out how many litres of water the vase holds when full. Give your answer to 1 decimal place.

    \(1\) litre \(= 1000\) cm³

    Show answer
    \(4.9\ \text{litres}\)
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  6. Calculator 4 marks

    A light shade is made from card stretched around the curved surface of a frustum. It is open at both ends.

    18 cm6 cm36 cm

    The frustum was cut from a cone of slant height \(54\) cm. Its two circular ends have radii \(18\) cm and \(6\) cm.

    Curved surface area of a cone \(= \pi r l\), where \(l\) is the slant height.

    Find the area of card needed. Give your answer to 1 decimal place.

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    \(2714.3\ \text{cm}^2\)
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  7. Either paper 3 marks

    The diagram shows a frustum. It was made by standing a cone on its base and slicing a smaller cone off the top, parallel to the base.

    20 cm12 cm4 cm

    The frustum has base radius \(12\) cm, top radius \(4\) cm and height \(20\) cm.

    Calculate the height of the cone that was removed.

    Show answer
    \(10\ \text{cm}\)
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  8. Either paper 4 marks

    A cone of height \(36\) cm and base radius \(6\) cm had a smaller cone sliced off the top, parallel to the base. The solid left behind is the frustum shown.

    6 cm4 cm

    The top of the frustum is a circle of radius \(4\) cm, and the cone that was removed is \(24\) cm tall.

    Volume of a cone \(= \frac{1}{3}\pi r^2 h\)

    Calculate the volume of the frustum. Give your answer in terms of \(\pi\).

    Show answer
    \(304\pi\ \text{cm}^3\)
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  9. Either paper 5 marks

    A solid cone has base radius \(18\) cm and height \(54\) cm.

    A cone of height \(24\) cm is removed from the top of it, by cutting parallel to the base. The solid left behind is the frustum shown.

    30 cm18 cm

    Volume of a cone \(= \frac{1}{3}\pi r^2 h\)

    (a)

    Work out the radius of the circular top of the frustum.

    (b)

    Work out the volume of the frustum. Give your answer in terms of \(\pi\).

    Show answer
    (a) \(8\ \text{cm}\)
    (b) \(5320\pi\ \text{cm}^3\)
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  10. Either paper 4 marks

    Here is a frustum, made by slicing a smaller cone off the top of a cone of slant height \(60\) cm.

    20 cm8 cm36 cm

    The base radius is \(20\) cm and the top radius is \(8\) cm.

    Curved surface area of a cone \(= \pi r l\), where \(l\) is the slant height.

    Calculate the curved surface area of the frustum. Give your answer in terms of \(\pi\).

    Show answer
    \(1008\pi\ \text{cm}^2\)
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discia.org Frustums · sheet 1
Answers Frustums · sheet 1
  1. \(8\ \text{cm}\)
  2. \(5805\pi\ \text{cm}^3\)
  3. (a) \(6\ \text{cm}\)
    (b) \(3159\pi\ \text{cm}^3\)
  4. \(1125\pi\ \text{cm}^2\)
  5. \(4.9\ \text{litres}\)
  6. \(2714.3\ \text{cm}^2\)
  7. \(10\ \text{cm}\)
  8. \(304\pi\ \text{cm}^3\)
  9. (a) \(8\ \text{cm}\)
    (b) \(5320\pi\ \text{cm}^3\)
  10. \(1008\pi\ \text{cm}^2\)
discia.org Frustums · sheet 1