Topic 6 of 8 · Grade 7
Shapes, area and volume
Acute (less than 90°), right (90°), obtuse (between 90° and 180°), straight (180°), reflex (more than 180°). Angles in a triangle add up to 180°; on a straight line to 180°; around a point to 360°.
Notes for this topic 1 file, in order
Create a free account to download PDFs.
Angles
Acute (less than 90°), right (90°), obtuse (between 90° and 180°), straight (180°), reflex (more than 180°). Angles in a triangle add up to 180°; on a straight line to 180°; around a point to 360°.
Worked example: Two angles of a triangle are 50° and 70°. Find the third angle.
180 − 50 − 70 = 60°
Shapes
Triangles (equilateral, isosceles, scalene, right-angled), quadrilaterals (square, rectangle, parallelogram, rhombus, trapezium), circles (radius, diameter, circumference), 3D shapes (cube, cuboid, cylinder, cone, sphere, pyramid) – faces, edges and vertices.
Perimeter and area
- Perimeter is the distance around a shape.
- Area of a rectangle = length × width; of a square = side × side; of a triangle = ½ × base × height.
Worked example: A garden is 12 m long and 8 m wide. Find its perimeter and area.
Perimeter = 12 + 8 + 12 + 8 = 40 m; area = 12 × 8 = 96 m²
Volume
Volume of a cube or cuboid = length × width × height (cm³ or m³).
Worked example: Find the volume of a box 10 cm long, 6 cm wide and 4 cm high.
10 × 6 × 4 = 240 cm³
Check yourself
- How many edges does a cube have?
- Find the area of a triangle with base 10 cm and height 6 cm.
- What is an obtuse angle?
Show answers
- 12
- 30 cm²
- An angle between 90° and 180°.
Questions about this topic (0)
No questions about this topic yet.
Sign in or create a free account to join in.