Grade 10 Mathematics
Grade 10 · Term 4Mathematics

Measurement

We revise surface area and volume of right prisms and cylinders, then extend to spheres, right pyramids and right cones. We also explore what happens to surface area and volume when any dimension is multiplied by a constant factor k.

Week 1

11.1 Surface Area & Volume of 3D Solids

  • Revise surface area and volume of right prisms and cylinders
  • Calculate surface area and volume of spheres, right pyramids and right cones
  • Study the effect on volume and surface area when any dimension is multiplied by factor k
  • Solve problems involving composite solids
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Real-World Connection

A manufacturer designing a tin can needs surface area to know how much metal to buy, and volume to know how much product it holds. Getting these formulas right is worth millions in material savings across a production run of millions of units.

Volume of a right prism

V=Abase×hV = A_{\text{base}} \times h

$A_{\text{base}}$ = area of the base (any shape); $h$ = perpendicular height

Surface area of a right prism

SA=2Abase+Pbase×hSA = 2A_{\text{base}} + P_{\text{base}} \times h

$P_{\text{base}}$ = perimeter of base; $h$ = height; 2 bases + lateral faces

Surface area of cylinder

SA=2πr2+2πrhSA = 2\pi r^2 + 2\pi r h

$r$ = radius, $h$ = height; two circular ends + curved surface

Volume of cylinder

V=πr2hV = \pi r^2 h

Special right prism with circular base: $A_{\text{base}} = \pi r^2$

ℹ️ Note

A cylinder is a right prism with a circular base. Substituting Abase=πr2A_{\text{base}}=\pi r^2 and Pbase=2πrP_{\text{base}}=2\pi r into the general right-prism formulas gives the cylinder formulas directly: V=πr2hV=\pi r^2 h and SA=2πr2+2πrhSA=2\pi r^2+2\pi r h. Similarly, a cone is a right pyramid with a circular base.

Surface area of sphere

SA=4πr2SA = 4\pi r^2

$r$ = radius

Volume of sphere

V=43πr3V = \frac{4}{3}\pi r^3

$r$ = radius

Volume of a right pyramid

V=13Abase×hV = \frac{1}{3} A_{\text{base}} \times h

$A_{\text{base}}$ = area of base; $h$ = perpendicular height from base to apex

Surface area of a square pyramid

SA=b2+2blSA = b^2 + 2bl

$b$ = base edge length; $l$ = slant height of each triangular face; 1 square base + 4 triangular faces

Volume of cone

V=13πr2hV = \frac{1}{3}\pi r^2 h

Right pyramid with circular base: $A_{\text{base}} = \pi r^2$

Slant height (cone or pyramid)

l=r2+h2l = \sqrt{r^2 + h^2}

$l$ = slant height from Pythagoras; $r$ = distance from centre of base to midpoint of base edge (or radius for cone)

Surface area of cone

SA=πr2+πrlSA = \pi r^2 + \pi r l

Base circle + lateral surface; $l$ = slant height

Property / Rule

Effect of scale factor k

If every dimension of a solid is multiplied by k: all lengths scale by k, all areas (surface area) scale by k², all volumes scale by k³.

SAnew=k2SAoldVnew=k3VoldSA_{\text{new}} = k^2 \cdot SA_{\text{old}}\qquad V_{\text{new}} = k^3 \cdot V_{\text{old}}
Worked Examples

Worked Example

Triangular prism — surface area and volume

Problem

A right triangular prism has an equilateral triangle base with side 6 cm and prism height 10 cm. Find the total surface area and volume.

Worked Example

Cylinder surface area and volume

Problem

Find the total surface area and volume of a cylinder with radius 5 cm and height 12 cm. Leave answers in terms of π\pi.

Worked Example

Composite solid — cone on cylinder

Problem

A solid has a cylinder (r=4r=4, h=10h=10) topped by a cone (r=4r=4, h=6h=6). Find total volume.

Worked Example

Square-based right pyramid

Problem

A square pyramid has base edge b=8b=8 cm and perpendicular height h=3h=3 cm. Find the slant height, total surface area and volume.

Worked Example

Effect of scale factor

Problem

A sphere has radius 3 cm. A larger sphere has radius 6 cm (scale factor k=2k=2). Compare their surface areas and volumes.
Activity — 8 Questions

CAPS Cognitive Level Distribution

L1 · Knowledge2 Q
L2 · Routine Procedures2 Q
L3 · Complex Procedures2 Q
L4 · Problem Solving2 Q
1
L1 · Knowledge1 mark
State the formula for the volume of a sphere.
2
L1 · Knowledge2 marks
Find the volume of a cube with side length 5 cm.
3
L2 · Routine Procedures3 marks
A square pyramid has base edge b=6b=6 cm and slant height l=5l=5 cm. Find the total surface area.
4
L2 · Routine Procedures3 marks
A cone has r=3r=3 cm and slant height l=5l=5 cm. Find total surface area.
5
L3 · Complex Procedures3 marks
A cylinder has volume 200π200\pi cm³ and height 8 cm. Find the radius.
6
L3 · Complex Procedures3 marks
All dimensions of a rectangular box are tripled (k = 3). By what factor does the volume increase? By what factor does the surface area increase?
7
L4 · Problem Solving5 marks
A hemisphere (flat face down) is placed on top of a cylinder of the same radius r=6r=6 cm and cylinder height h=10h=10 cm. Find total volume.
8
L4 · Problem Solving5 marks
A sphere just fits inside a cube of side 8 cm. What percentage of the cube's volume does the sphere occupy? (Give answer to 1 decimal place.)
Measurement Grade 10 Maths CAPS Notes & Examples | MathSciBuddy