# Name the Triangle

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

Key stage:  KS 3

Curriculum topic:   Geometry and Measures

Curriculum subtopic:   Apply Facts About Angles and Sides

Difficulty level:

### 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 34º and 112º.  Which type of triangle is it?

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

180º - (34º + 112º) = 180º - 146º = 34º

So the triangle has angles 34º , 112º, 34º

Two angles are equal so it is isosceles.

Two of the angles in a triangle are  96º  and   42º

Which type of triangle is it?

scalene

right-angled

isosceles

equilateral

Two of the angles in a triangle are  42º  and   48º

Which type of triangle is it?

isosceles

right-angled

scalene

equilateral

Two of the angles in a triangle are  55º  and   80º

Which type of triangle is it?

isosceles

right-angled

scalene

equilateral

Two of the angles in a triangle are  57º  and   33º

Which type of triangle is it?

isosceles

right-angled

scalene

equilateral

Two of the angles in a triangle are  16º  and   148º

Which type of triangle is it?

isosceles

right-angled

scalene

equilateral

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

Which type of triangle is it?

isosceles

right-angled

scalene

equilateral

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

Which type of triangle is it?

isosceles

right-angled

scalene

equilateral

Two of the angles in a triangle are  44º  and   103º

Which type of triangle is it?

isosceles

right-angled

scalene

equilateral

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

Which type of triangle is it?

isosceles

right-angled

scalene

equilateral

Two of the angles in a triangle are    and   178º

Which type of triangle is it?

isosceles

right-angled

scalene

equilateral

• Question 1

Two of the angles in a triangle are  96º  and   42º

Which type of triangle is it?

isosceles
• Question 2

Two of the angles in a triangle are  42º  and   48º

Which type of triangle is it?

right-angled
• Question 3

Two of the angles in a triangle are  55º  and   80º

Which type of triangle is it?

scalene
• Question 4

Two of the angles in a triangle are  57º  and   33º

Which type of triangle is it?

right-angled
• Question 5

Two of the angles in a triangle are  16º  and   148º

Which type of triangle is it?

isosceles
• Question 6

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

Which type of triangle is it?

equilateral
• Question 7

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

Which type of triangle is it?

right-angled
• Question 8

Two of the angles in a triangle are  44º  and   103º

Which type of triangle is it?

scalene
• Question 9

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

Which type of triangle is it?

right-angled
• Question 10

Two of the angles in a triangle are    and   178º

Which type of triangle is it?

isosceles
---- OR ----

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