Formalising understanding of triangles from KS2 | Maths

Starter quiz

TU is a line segment. $a$ ° = ______°.
- '37' ✓
These three angles lie around a point on a full turn. $b$ ° = ______°.
- '54' ✓
This diagram shows four angles around two line segments that meet at an intersection. Which of these statements are correct for angle $c$ °?
- Angle $c$ ° and 42° are vertically opposite.
- Angle $c$ ° and 42° are supplementary. ✓
- Angle $c$ ° and 42° are conjugate.
- Angle $c$ ° is 42°.
- Angle $c$ ° is 138°. ✓
This diagram shows four angles around two line segments that meet at an intersection. Which of these statements are correct for angle $d$ ?
- Angle $d$ ° and 42° are vertically opposite. ✓
- Angle $d$ ° and 42° are supplementary.
- Angle $d$ ° and 42° are conjugate.
- Angle $d$ ° is 42°. ✓
- Angle $d$ ° is 318°.
PQ and RS are straight line segments. $e$ ° = ______°.
- '111' ✓
PQ and RS are straight line segments. Match each angle to its size.
- $f$ °
  
  ⇔
  
  155° ✓
- $g$ °
  
  ⇔
  
  25° ✓
- $h$ °
  
  ⇔
  
  65° ✓
- right angle
  
  ⇔
  
  90° ✓
- not an angle on the diagram
  
  ⇔
  
  45° ✓
- sum of angles on the diagram
  
  ⇔
  
  360° ✓

Which of these statements are true about this triangle?
- It is a scalene triangle. ✓
- It is a right angle triangle.
- $a$ ° = 61°
- $a$ ° = 82° ✓
- $a$ ° = 90°
This triangle is scalene. Which of these are possible values of $b$ ?
- 5
- 6
- 9 ✓
- 14
- 16 ✓
Which of these statements are correct for this triangle?
- The triangle is scalene.
- The triangle is isosceles. ✓
- The triangle is right angle.
- $c$ ° = 48° ✓
- It is impossible to know the size of angle $c$ .
An equilateral triangle has one side of length 40 cm. Which of these statements are correct?
- It is impossible to know any angles in this triangle, as none are given.
- All interior angles are 60°. ✓
- A different side of this triangle has a length of 40 cm. ✓
- A different side of this triangle has a length of 60 cm.
- The perimeter of the triangle is 120 cm. ✓
An isosceles triangle has an angle of 90°, and a side of length 19 cm. What is the size of one of its other angles, in degrees? ______°.
- '45' ✓
Three different triangles each have an angle of 30°. Match the name of each triangle to their possible angles.
- isosceles
  
  ⇔
  
  another angle of 30° and one of 120° ✓
- scalene
  
  ⇔
  
  one angle of 77° and another 73° ✓
- right-angled scalene
  
  ⇔
  
  an angle of 60° and one of 90° ✓
- equilateral
  
  ⇔
  
  impossible to have this triangle with an angle of 30° ✓

Loading worksheet ...

Loading presentation ...

An equilateral triangle is a regular triangle and has particular properties.
A scalene triangle has specific properties.
An isosceles triangle has properties including a line of symmetry that splits it into two congruent triangles.
A right-angled triangle can be scalene or isosceles.

The horizontal side length of an isosceles triangle is always the base side.

The base side of an isosceles triangle can have any orientation. It is important to look at the hash marks, angle markers, or measurements.

Equilateral - Equilateral triangles have three equal-sized angles and three edges of equal length. They are regular triangles.
Scalene - Scalene triangles have three different-sized angles and three different-sized edges (sides).
Isosceles - Isosceles triangles have two equal-sized angles and two sides of the same length.
Right-angled triangle - A right-angled triangle has exactly one 90° interior angle.