New
New
Year 5

Measure the size of angles accurately using a protractor

I can measure the size of angles accurately using a protractor.

New
New
Year 5

Measure the size of angles accurately using a protractor

I can measure the size of angles accurately using a protractor.

Lesson details

Key learning points

  1. A protractor is an angle measurer.
  2. Protractors have two scales from 0 to 180 degrees.
  3. Start from zero when reading the scale on a protractor.
  4. Line the protractor up with one of the lines forming the angle.

Common misconception

Pupils incorrectly place the protractor on the angle and therefore cannot measure the angle. Pupils use the incorrect scale to read the angle.

Stress the importance of using the middle spot on the protractor to line this up with the vertex of the angle as well as placing one of the lines on a zero line, ensuring the remaining line crosses the scale of the protractor.

Keywords

  • Angle - An angle is a measure of turn. It shows how far something has rotated. It is often displayed as the rotation between two line segments.

  • Point - A point is an exact location. It has no size, only position.

  • Vertex - A vertex is a point where two or more lines meet.

  • Scale - A scale is a number line with equal divisions for equal values.

Encourage pupils to explain how other pupils have incorrectly attempted to measure an angle using a protractor. Highlighting these misconceptions can benefit everyone in deepening their understanding for how to measure using a protractor.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
Match the shape to its properties.
Correct Answer:Equilateral triangle,A triangle with three equal sides and three equal vertices.

A triangle with three equal sides and three equal vertices.

Correct Answer:Isosceles triangle,A triangle with two equal sides and two equal vertices.

A triangle with two equal sides and two equal vertices.

Correct Answer:Scalene triangle ,A triangle with no equal sides or vertices.

A triangle with no equal sides or vertices.

Q2.
Which of these is the best estimate for the angle shown?
An image in a quiz
150°
180°
Correct answer: 220°
300°
Q3.
The image is not to scale. What is the value of missing angle a? a = °
An image in a quiz
Correct Answer: 83
Q4.
Which of these is the best estimate for the angle shown?
An image in a quiz
85°
100°
Correct answer: 175°
180°
Q5.
The image is not to scale. Calculate missing angle a. a = °
An image in a quiz
Correct Answer: 68
Q6.
The image is not to scale. Complete the sentence. I estimate that the size of angle a is ___ degrees.
An image in a quiz
85
90
Correct answer: 95
Correct answer: 100

6 Questions

Q1.
Which image shows the protractor placed correctly to measure the angle?
An image in a quiz
An image in a quiz
Correct Answer: An image in a quiz
An image in a quiz
Q2.
The size of the angle is ___.
An image in a quiz
155°
140°
55°
Correct answer: 35°
Q3.
Read the protractor scale to measure the angle. °
An image in a quiz
Correct Answer: 80°
Q4.
Read the protractor scale to measure the angle. °
An image in a quiz
155°
145°
45°
Correct answer: 55°
Q5.
Sofia measured the obtuse angle in order to find the missing angle a. What is her next step?
An image in a quiz
Subtract 115 from 180
Correct answer: Subtract 115 from 360
Double 115
Guess the size of a based on the angle of 115°
Q6.
Jun measured the acute angle in order to find the missing angle a. Tick what his next steps could be.
An image in a quiz
Correct answer: Subtract 43 from 180
Subtract 43 from 360
Add 43 with 180, then subtract from 360
Subtract 180 then subtract 43 from 360