Learning Objectives
- Calculate the area of parallelograms and triangles
- Find the circumference and area of circles
- Convert between units of area
- Solve problems involving composite shapes
Key Concepts
Area of Parallelogram
Area = Base × Height
The height is the perpendicular distance between the base and its opposite side.
Area of Triangle
Area = ½ × Base × Height
A triangle is half of a parallelogram with the same base and height.
Circles
Circumference = 2πr = πd (where r = radius, d = diameter)
Area = πr²
π ≈ 22/7 or 3.14
Area Conversions
1 m² = 10,000 cm²
1 hectare = 10,000 m²
1 km² = 100 hectares
Summary
Area is measured in square units. Parallelogram area depends on base and height. Triangle area is half of the parallelogram. Circle calculations use π. For composite shapes, break them into simpler shapes and add or subtract areas.
Important Terms
- Perimeter
- The total distance around the boundary of a shape
- Area
- The amount of space enclosed within a shape, measured in square units
- Circumference
- The perimeter of a circle
- Radius
- The distance from the centre of a circle to any point on the circle
- Diameter
- A chord passing through the centre; d = 2r
Quick Revision
- Area of rectangle = length × breadth
- Area of parallelogram = base × height
- Area of triangle = ½ × base × height
- Circumference of circle = 2πr
- Area of circle = πr²
- π ≈ 22/7 ≈ 3.14
Practice Tips
- Measure real objects (tables, rooms, wheels) to calculate areas and perimeters
- Practice breaking complex shapes into rectangles, triangles, and circles
- Always include units in your final answer