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G17

Know circumference of a circle = 2πr = πd and area = πr²; calculate perimeters of 2D shapes incl. circles, areas of circles and composite shapes, surface area and volume of spheres, pyramids, cones

Circle and 3D mensuration

Worked answers, methods and verified real exam appearances for G17 on Edexcel GCSE Maths 1MA1.

Explanation

  • For a circle, use C=2πr=πdC=2\pi r=\pi d and A=πr2A=\pi r^2. Composite areas add included regions and subtract cut-outs; composite perimeters include only the outside boundary.
  • A cone or pyramid has volume V=13×base area×perpendicular heightV=\frac13\times\text{base area}\times\text{perpendicular height}. A cone's curved surface area is πrl\pi rl, where ll is slant height.
  • A sphere has surface area 4πr24\pi r^2 and volume 43πr3\frac43\pi r^3.
  • For a composite solid, divide it into recognised solids and exclude internal joined faces from surface area.
  • Examiners expect radius, perpendicular height and slant height to be distinguished correctly.
A cone's perpendicular height hh and slant height ll have different roles.

Worked example

A solid cone has radius 33 cm, perpendicular height 44 cm and slant height 55 cm. Find its total surface area and volume in terms of π\pi.

  1. 1.Curved area =πrl=π(3)(5)=15π cm2=\pi rl=\pi(3)(5)=15\pi\text{ cm}^2; base area =πr2=9π cm2=\pi r^2=9\pi\text{ cm}^2.
  2. 2.Total surface area =15π+9π=24π cm2=15\pi+9\pi=24\pi\text{ cm}^2.
  3. 3.Volume =13πr2h=13π(32)(4)=12π cm3=\frac13\pi r^2h=\frac13\pi(3^2)(4)=12\pi\text{ cm}^3.

Answer: Total surface area =24π cm2=24\pi\text{ cm}^2; volume =12π cm3=12\pi\text{ cm}^3.

Common mistakes

  • Don't use the slant height ll in the cone-volume formula instead of the perpendicular height hh.
  • Don't add the circular base twice or omit it when total surface area is requested.

Exam tip

Underline 'curved' or 'total' surface area, then list the exposed faces before calculating.

Worked practice

Q1
Tier 1 · Easy

1

A circle has diameter 13 cm13\text{ cm}. Write its circumference in terms of π\pi.

(1)

(Total for Question 1 is 1 mark)

Mark scheme

Mark scheme for question 1
QuestionAnswerMarkMark scheme
1
  • 13π cm13\pi\text{ cm}
1Use C=πdC=\pi d. With d=13 cmd=13\text{ cm}, the circumference is 13π cm13\pi\text{ cm}.
Q2
Tier 2 · Standard

2

A semicircle of diameter 10 cm10\text{ cm} is attached to one of the shorter sides of an 18 cm18\text{ cm} by 10 cm10\text{ cm} rectangle. The shared diameter is inside the shape. Work out the area and perimeter of the composite shape in terms of π\pi.

(4)

(Total for Question 2 is 4 marks)

Mark scheme

Mark scheme for question 2
QuestionAnswerMarkMark scheme
2
  • Area =180+25π2 cm2=180+\frac{25\pi}{2}\text{ cm}^2
  • Perimeter =46+5π cm=46+5\pi\text{ cm}
4The rectangle area is 18×10=180 cm218\times10=180\text{ cm}^2. The semicircle has radius 5 cm5\text{ cm}, so its area is 12π(52)=25π2 cm2\frac12\pi(5^2)=\frac{25\pi}{2}\text{ cm}^2. For the perimeter, include the two 18 cm18\text{ cm} sides, the unshared 10 cm10\text{ cm} side and the semicircular arc πr=5π cm\pi r=5\pi\text{ cm}. This gives area 180+25π2 cm2180+\frac{25\pi}{2}\text{ cm}^2 and perimeter 46+5π cm46+5\pi\text{ cm}.
Q3
Tier 3 · Hard

3

A solid cone has radius 6 cm6\text{ cm}, perpendicular height 8 cm8\text{ cm} and slant height 10 cm10\text{ cm}. Work out its total surface area, including the circular base, and its volume. Give both answers in terms of π\pi.

(5)

(Total for Question 3 is 5 marks)

Mark scheme

Mark scheme for question 3
QuestionAnswerMarkMark scheme
3
  • Total surface area =96π cm2=96\pi\text{ cm}^2
  • Volume =96π cm3=96\pi\text{ cm}^3
5The curved surface area is πrl=π(6)(10)=60π cm2\pi rl=\pi(6)(10)=60\pi\text{ cm}^2 and the base area is πr2=36π cm2\pi r^2=36\pi\text{ cm}^2, giving 96π cm296\pi\text{ cm}^2 in total. The volume is 13πr2h=13π(62)(8)=96π cm3\frac13\pi r^2h=\frac13\pi(6^2)(8)=96\pi\text{ cm}^3.
Q4
Tier 1 · Easy

4

A circle has radius 6 cm6\text{ cm}. Work out its area in terms of π\pi.

(1)

(Total for Question 4 is 1 mark)

Mark scheme

Mark scheme for question 4
QuestionAnswerMarkMark scheme
4
  • 36π cm236\pi\text{ cm}^2
1Use A=πr2A=\pi r^2. Therefore A=π(62)=36π cm2A=\pi(6^2)=36\pi\text{ cm}^2.
Q5
Tier 2 · Standard

5

A square has side length 11 cm11\text{ cm}. A circular hole of radius 4 cm4\text{ cm} is cut from the square. Work out the area that remains in terms of π\pi.

(2)

(Total for Question 5 is 2 marks)

Mark scheme

Mark scheme for question 5
QuestionAnswerMarkMark scheme
5
  • 12116π cm2121-16\pi\text{ cm}^2
2The square has area 112=121 cm211^2=121\text{ cm}^2. The circular hole has area π(42)=16π cm2\pi(4^2)=16\pi\text{ cm}^2. Therefore the remaining area is 12116π cm2121-16\pi\text{ cm}^2.
Q6
Tier 3 · Hard

6

The total surface area of a solid hemisphere, including its circular base, is 147π cm2147\pi\text{ cm}^2. Work out the volume of the hemisphere in terms of π\pi.

(4)

(Total for Question 6 is 4 marks)

Mark scheme

Mark scheme for question 6
QuestionAnswerMarkMark scheme
6
  • 686π3 cm3\frac{686\pi}{3}\text{ cm}^3
4The curved surface area of a hemisphere is 2πr22\pi r^2 and its circular base has area πr2\pi r^2, so 3πr2=147π3\pi r^2=147\pi. Hence r2=49r^2=49 and r=7 cmr=7\text{ cm}. The volume is half the volume of a sphere, so V=23πr3=23π(73)=686π3 cm3V=\frac23\pi r^3=\frac23\pi(7^3)=\frac{686\pi}{3}\text{ cm}^3.
Q7
Tier 2 · Standard

7

A circle has radius 8 cm8\text{ cm}. A square has the same perimeter as the circle. Work out the area of the square in terms of π\pi.

(3)

(Total for Question 7 is 3 marks)

Mark scheme

Mark scheme for question 7
QuestionAnswerMarkMark scheme
7
  • 16π2 cm216\pi^2\text{ cm}^2
3The circle has perimeter 2π(8)=16π cm2\pi(8)=16\pi\text{ cm}. Each side of the square is 16π÷4=4π cm16\pi\div4=4\pi\text{ cm}. Therefore the square has area (4π)2=16π2 cm2(4\pi)^2=16\pi^2\text{ cm}^2.
Q8
Tier 3 · Hard

8

A circular pond has radius 7 m7\text{ m}. A path surrounds the pond. The outer edge of the path is a circle with circumference 18π m18\pi\text{ m}. Work out the area of the path in terms of π\pi.

(4)

(Total for Question 8 is 4 marks)

Mark scheme

Mark scheme for question 8
QuestionAnswerMarkMark scheme
8
  • 32π m232\pi\text{ m}^2
4For the outer circle, 2πR=18π2\pi R=18\pi, so R=9 mR=9\text{ m}. The outer area is 81π m281\pi\text{ m}^2 and the pond area is 49π m249\pi\text{ m}^2. Therefore the path area is 81π49π=32π m281\pi-49\pi=32\pi\text{ m}^2.
Q9
Tier 3 · Hard

9

Higher only: A solid hemisphere of radius 5 cm5\text{ cm} is joined along its circular face to the circular base of a cone. The cone also has radius 5 cm5\text{ cm} and has slant height 13 cm13\text{ cm}. The joined circular faces are inside the solid. Work out the exterior surface area of the solid in terms of π\pi.

(4)

(Total for Question 9 is 4 marks)

Mark scheme

Mark scheme for question 9
QuestionAnswerMarkMark scheme
9
  • 115π cm2115\pi\text{ cm}^2
4Only the curved surfaces are exposed. The curved surface area of the hemisphere is 2πr2=2π(52)=50π cm22\pi r^2=2\pi(5^2)=50\pi\text{ cm}^2. The curved surface area of the cone is πrl=π(5)(13)=65π cm2\pi rl=\pi(5)(13)=65\pi\text{ cm}^2. Therefore the exterior surface area is 50π+65π=115π cm250\pi+65\pi=115\pi\text{ cm}^2.
Q10
Tier 3 · Hard

10

Higher only: A pyramid has a trapezium as its base. The parallel sides of the trapezium are 8 cm8\text{ cm} and 14 cm14\text{ cm}, and the perpendicular distance between them is 6 cm6\text{ cm}. The volume of the pyramid is 330 cm3330\text{ cm}^3. Work out the perpendicular height of the pyramid.

(4)

(Total for Question 10 is 4 marks)

Mark scheme

Mark scheme for question 10
QuestionAnswerMarkMark scheme
10
  • 15 cm15\text{ cm}
4The base area is 12(8+14)×6=66 cm2\frac12(8+14)\times6=66\text{ cm}^2. If the perpendicular height is h cmh\text{ cm}, then 330=13×66×h=22h330=\frac13\times66\times h=22h. Therefore h=15 cmh=15\text{ cm}.

Verified exam appearances

SeriesPaperQuestionMarksCalculatorTierLinks
2019-061FQ284Non-calculatorFoundationQPMS
2023-113HQ194AllowedHigherQPMS
2021-112FQ254AllowedFoundationQPMS
2019-063HQ65AllowedHigherQPMS
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2023-061HQ164Non-calculatorHigherQPMS
2022-111HQ246Non-calculatorHigherQPMS
2023-111HQ103Non-calculatorHigherQPMS
2022-061HQ133Non-calculatorHigherQPMS
2019-113FQ303AllowedFoundationQPMS
2024-063HQ214AllowedHigherQPMS
2019-113HQ235AllowedHigherQPMS
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2023-113FQ294AllowedFoundationQPMS
2022-112FQ215AllowedFoundationQPMS
2023-062HQ124AllowedHigherQPMS
2019-063FQ295AllowedFoundationQPMS
2021-113FQ274AllowedFoundationQPMS
2022-112HQ45AllowedHigherQPMS
2024-061FQ124Non-calculatorFoundationQPMS
2019-061HQ74Non-calculatorHigherQPMS
2024-112FQ103AllowedFoundationQPMS
2019-113FQ142AllowedFoundationQPMS
2019-112HQ192AllowedHigherQPMS
2019-061HQ154Non-calculatorHigherQPMS
2019-063FQ163AllowedFoundationQPMS
2021-111HQ74Non-calculatorHigherQPMS
2024-063HQ93AllowedHigherQPMS
2024-113HQ113AllowedHigherQPMS

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