Learning objectives
Identify shapes and calculate simple geometric measurements.
By the end of this course, you should be able to explain the key ideas, use the methods and answer practice questions.
Lesson notes
Lines and angles
An acute angle is less than 90°. A right angle is 90°. An obtuse angle is greater than 90° but less than 180°.
Triangles
A triangle has three sides. The interior angles of a triangle add up to 180°.
Quadrilaterals
A quadrilateral has four sides. A rectangle has four right angles.
Perimeter
Perimeter is the distance around a shape. For a rectangle, P = 2 × (length + width).
Area
The area of a rectangle is length × width. A rectangle 5 cm by 3 cm has area 15 cm².
Worked example
A rectangle 8 cm long and 3 cm wide has area 8 × 3 = 24 cm².
Practice quiz
Enter an answer for each question. Then select Check answers. For fractions, use forms such as 1/2.