Use the terms acute, obtuse and reflex when comparing angles to a right angle | Maths

Starter quiz

Look at the image. This shape has ______ right angles.
- '2' ✓
This shape has one pair of parallel sides. True or false?
- True ✓
- False
Complete the sentence. A parallelogram has ______ vertices.
- '4' ✓
Match the shape to its properties.
- square
  
  ⇔
  
  A polygon with four equal sides and four right angles. ✓
- triangle
  
  ⇔
  
  A polygon with three sides and three vertices. ✓
- pentagon
  
  ⇔
  
  A polygon with five sides and five vertices. ✓
The minute hand shows 4 o’clock. The minute hand moves a quarter turn clockwise. What time is shown?
- Quarter past 4 ✓
- Half past 4
- Quarter to 5
- 5 o’clock
Which of the angles shown is the smallest?
- A
- B ✓
- C

Exit quiz

Which type of angle is shown?
- Acute
- Right
- Obtuse ✓
- Reflex
Which type of angle is shown?
- Acute ✓
- Right
- Obtuse
- Reflex
Look at the hands on this clock face and the arrow. The angle formed is __________.
- Acute
- A right angle
- Obtuse ✓
- Reflex
Look at the hands on this clock face and the arrow. The angle formed is __________.
- Acute
- A right angle
- Obtuse
- Reflex ✓
This is a trapezium. Look carefully at the vertices and the angles inside the shape. Complete the sentence. There are ______ acute angles in the trapezium.
- '2' ✓
This is a trapezium. Look carefully at the vertices and the angles inside the shape. Which statement is correct?
- The trapezium has four obtuse angles.
- The trapezium has two right angles and two acute angles.
- The trapezium has two right angles and two obtuse angles.
- The trapezium has two right angles, one acute angle and one obtuse angle. ✓

Worksheet

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Lesson Details

Key learning points

Angles are marked with a curve between the lines which have been rotated
Angles with a bigger turn are larger than those with a smaller turn
Angles can be bigger than a right ange or smaller than a right angle

Common misconception

Angles must always be formed with one horizontal line. Angles must also have two straight lines that are exactly the same length.

Provide pupils with examples where acute, obtuse and reflex angles are shown in a wide range of orientations and where the length of the lines leading into the angles differ in size to support generalising the features of each angle type.

Keywords

Angle - An angle is a measure of turn. It shows how far something has rotated.
Right angle - A right angle is a square corner or a quarter turn.
Acute angle - An angle that is smaller than a right angle is an acute angle.
Obtuse angle - An angle that is greater than a right angle but smaller than a straight line is an obtuse angle.
Reflex angle - An angle that is greater than a straight line up to a full turn is a reflex angle.