Types Of Triangles

Shapes in geometry are typically divided into 2D and 3D shapes. Children in the age range of 9 to 11 learn about basic concepts of geometry like lines, angles, circles, nets of 3D shapes, and triangles.

Three-sided, two-dimensional figures with internal angles of 180 degrees are referred to as triangles. In this guide, we will further study triangles and their types.

This teaching guide unravels the various types of triangles through a stimulating animated comic story, vibrant posters, intriguing worksheets, and engaging activities.

Triangles are categorised into various subtypes based on the length of their sides and the measure of their interior angles.

Website - Gumroad 9 To 11 CTA Banner

Triangles can be classified into the following types, on the basis of the sides of the triangles : 

  1. Equilateral Triangle:
    • All three sides of an equilateral triangle are equal in length.
    • All three angles in an equilateral triangle are equal and measure 60 degrees.
    • It is a type of regular polygon.
  1. Isosceles Triangle :
    • An isosceles triangle has two sides of equal length.
    • The angles opposite the equal sides are congruent.
    • The third angle, opposite the unequal side, is called the base angle.
  1. Scalene Triangle :
    • A scalene triangle has no sides of equal length.
    • All three angles in a scalene triangle have different measures.

Triangles can be classified into the following types, on the basis of the interior angles of the triangles :

  1. Right Triangle :
    • A right triangle has one angle measuring 90 degrees, known as a right angle.
    • The side opposite the right angle is called the hypotenuse.
    • The other two sides are called legs, and they can have different lengths.
  1. Acute Triangle :
    • An acute triangle has three angles that are less than 90 degrees.
    • All angles in an acute triangle are acute angles.
  1. Obtuse Triangle :
    • An obtuse triangle has one angle that is greater than 90 degrees.
    • The other two angles are acute angles.

Points to ponder about triangles  :

  • Each of the three internal angles in an equilateral triangle is 60 degrees.
  • Sum of all the three interior angles in a triangle is always equal to 180 degrees.
  • All triangles have two acute angles.
  • An equilateral or equiangular triangle is one in which all of its sides and angles are equal.
Uncle Math 9 to 11 Years App Banner
Uncle Math 9 to 11 Years App Banner


Teaching angles with kid-friendly, clear, and easy-to-understand posters from Uncle Math School by Fun2Do Labs :


Ignite kids’ curiosity with engaging stories for role play and skits, making the learning of this concept an exciting and effective experience. Teaching  angles through stories from Uncle Math School by Fun2Do Labs :

Text Of The Stories


Learning angles can be made enjoyable by incorporating interactive games and activities.

Matchstick Triangles!

  • Instruct children to make different types of triangles by using Matchsticks.
  • Later, they can observe and label their creation by categorising it into different types of triangles.


Help your kids practise  angles with interesting and engaging fun worksheets and solutions from Uncle Math by Fun2Do Labs.

Worksheet 680 : Types Of Triangles
Solution 680 : Types Of Triangles
Worksheet 681 : Types Of Triangles
Solution 681 : Types Of Triangles
Worksheet 682 : Types Of Triangles
Solution 682 : Types Of Triangles

Explore Related Guides :