Lines and Angles • Topic 3 of 3

Using a Protractor to Measure Angles

A protractor is the tool used to measure angles in degrees.

Steps to measure an angle with a protractor:

  • Place the centre hole of the protractor at the vertex of the angle
  • Align the baseline (0 line) with one ray of the angle
  • Read the degrees where the second ray crosses the scale
  • Use the scale that starts from 0 on the side where you placed the baseline

Protractors have two scales — always use the correct one!

Using a Protractor90 degrees1800Centre hole at vertex; baseline along one ray; read other ray
Solved Examples
1
Worked Example
Describe the steps to draw a 60 degree angle.
SolutionStep 1: Draw a ray. Step 2: Place protractor centre at the endpoint (vertex). Step 3: Align baseline with the ray. Step 4: Mark a point at 60 degrees on the scale. Step 5: Connect the vertex to that point with another ray.
2
Worked Example
A shape has 4 sides. All angles are 90 degrees. Opposite sides are parallel and equal. What shape is it?
SolutionA shape with 4 right angles, opposite sides parallel and equal is a Rectangle. If all four sides are also equal, it is a Square.
3
Worked Example
How many pairs of parallel lines does a rectangle have?
SolutionA rectangle has 2 pairs of parallel lines: the top and bottom sides are parallel, and the left and right sides are parallel.

Key Points

  • A protractor measures angles in degrees
  • Place centre hole at vertex, baseline along one ray, read where second ray points
  • Always use the scale that starts from 0 on the side of the first ray
  • Rectangles have 4 right angles (90 degrees) and 2 pairs of parallel sides
Quick Check — 4 MCQs
Tap an option to check your answer0 / 4
Q1.A protractor measures angles in:
Explanation: Degrees.
Q2.The centre of the protractor is placed on the:
Explanation: The vertex.
Q3.One arm should line up with the:
Explanation: Zero line.
Q4.A standard protractor reads from $0^\circ$ to:
Explanation: $180^\circ$.
Practice more MCQs → 📝 Assignment · 35 marks