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Geometry: Name the Triangle

In this worksheet, students work out the missing angle in a triangle in order to identify the type of triangle.

'Geometry: Name the Triangle' worksheet

Key stage:  KS 2

Curriculum topic:  Geometry: Properties of Shapes

Curriculum subtopic:  Compare Geometric Shapes

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

Remember that the interior angles of a triangle add up to 180º.

 

right-angled triangle has one 90º angle.

An isosceles triangle has two equal angles.

An equilateral triangle has three equal angles, each of size 60º

 

Example

Two of the angles in a triangle are 35º and 110º.  Which type of triangle is it?

 

Answer

We must first work out the third angle which will be:

180º - (35º + 110º) = 180º - 145º = 35º

 

So the triangle has angles 35º , 110º, 35º 

 

Two angles are equal so it is isosceles.

 

Two of the angles in a triangle are  70º  and   40º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  50º  and   40º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  50º  and   80º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  50º  and   60º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  30º  and   30º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  60º  and   60º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  45º  and   45º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  45º  and   75º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  56º  and   34º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  23º  and   134º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

  • Question 1

Two of the angles in a triangle are  70º  and   40º

Which type of triangle is it?

CORRECT ANSWER
isosceles
EDDIE SAYS
180 - 70 - 40 = 70 An isosceles triangles has two equal angles, which are 70 degrees in this problem.
  • Question 2

Two of the angles in a triangle are  50º  and   40º

Which type of triangle is it?

CORRECT ANSWER
right-angled
EDDIE SAYS
180 - 50 - 40 = 90 A right-angled triangle is 90 degrees.
  • Question 3

Two of the angles in a triangle are  50º  and   80º

Which type of triangle is it?

CORRECT ANSWER
isosceles
EDDIE SAYS
180 - 50 - 80 = 50 An isosceles triangle has two equal angles which are 50 degrees here.
  • Question 4

Two of the angles in a triangle are  50º  and   60º

Which type of triangle is it?

CORRECT ANSWER
scalene
EDDIE SAYS
180 - 50 - 60 = 70 A scalene triangle has three different angles.
  • Question 5

Two of the angles in a triangle are  30º  and   30º

Which type of triangle is it?

CORRECT ANSWER
isosceles
EDDIE SAYS
An isosceles triangle has two equal angles.
  • Question 6

Two of the angles in a triangle are  60º  and   60º

Which type of triangle is it?

CORRECT ANSWER
equilateral
EDDIE SAYS
An equilateral triangle has three equal angles that are all 60 degrees.
  • Question 7

Two of the angles in a triangle are  45º  and   45º

Which type of triangle is it?

CORRECT ANSWER
right-angled
EDDIE SAYS
180 - 45 - 45 = 90 A right-angled triangle has a 90 degree angle.
  • Question 8

Two of the angles in a triangle are  45º  and   75º

Which type of triangle is it?

CORRECT ANSWER
scalene
EDDIE SAYS
180 - 45 - 75 = 60 A scalene triangle has three different angles.
  • Question 9

Two of the angles in a triangle are  56º  and   34º

Which type of triangle is it?

CORRECT ANSWER
right-angled
EDDIE SAYS
180 - 56 - 34 = 90 A right-angled triangle has a 90 degree angle.
  • Question 10

Two of the angles in a triangle are  23º  and   134º

Which type of triangle is it?

CORRECT ANSWER
isosceles
EDDIE SAYS
180 - 23 - 134 = 23 An isosceles triangle has two equal angles.
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