Tips for Teaching How to Classify a Triangle

Similar to teaching how to classify quadrilaterals, teaching how to classify triangles may require you to approach the lesson from many different angles….or sides! To help reinforce the ways to classify triangles, be sure to provide your students with as many hands-on and unique learning activities as possible. Here are some fun tips and activities to use when teaching your students how to classify a triangle.

Tricks to Remembering the Types of Triangles

One of the trickiest parts of classifying triangles for some students may be knowing the definitions of the different terms. Students can easily confuse new terms like obtuse, isosceles, and scalene, so it’s best to help them think of ways to remember what each term means. These word associations can help students quickly remember the different terms and help them better understand how to classify a triangle.

Classifying Triangles by Angles

Acute triangles are triangles that all three angles are less than 90°. Since the angles are all “smaller” than 90°, you can suggest students think of this type of triangle as “a-cute little triangle”.

Obtuse triangles have one angle that is greater than 90°. When looking at an obtuse triangle, you can picture someone with open arms on one side of the triangle at the obtuse angle. Students can think of “obtuse-open” to help them remember this triangle type.

You can even go as far as saying “obtuse” in a loud, deep voice. You can even hold your arms out in a wide-angle as you say the word. This is a silly way to encourage students to make that connection that obtuse triangles are a large angle.

Right-angle triangles might be the easiest to remember if students are familiar with right angles. Holding up their right pointer finger and thumb to make a right angle or an L and then using their left pointer finger to complete the triangle is a great way to demonstrate a right triangle.

Classifying Triangles by Sides

Equilateral triangles have three equal sides. This term in itself should help students remember that this triangle is completely equal on all sides. When you introduce equilateral triangles, ask students to find a word inside that looks familiar to them. Just another way to help students make that connection that all three sides are equal.

Isosceles triangles have two equal sides. Encourage students to think of having two eyes and the word isosceles starts with the letter i. The word isosceles also has the two Ss in the front half of the word. Every time students write the word isosceles, have them underline the two Ss. This is a great way to remember that isosceles = 2 equal sides.

Scalene triangles might be the most difficult triangle to associate with anything. Since it’s the oddball term without any easy trick, students may think of scalene triangles as being just that – the odd triangle with three different length sides and three different angles.

Looking for hands-on, inquiry-based activities?

Once students have learned the different terms and definitions relating to classifying triangles, they will need lots of repetition and hands-on practice to master classifying triangles on their own. Here are some ways you can support them in the classroom with opportunities to practice identifying and classifying triangles.

Using Songs and Videos to Classify Triangles

Flocabulary has a fantastic music video on classifying triangles. This video walks through classifying triangles by the length of their sides and by the size of their angles. The visuals in this video are great and there are also some fun body motions that you can have your students do along with the video!

Encourage your students to stand during the video and do the motions along with the video to demonstrate acute, right, obtuse, isosceles, scalene, and equilateral triangles. (The motions are at the 1:50 and 3:10 marks in the video.)

The physical movements will offer a brain break and help students retain what they’re hearing in the video. You may even find them (or yourself) humming or singing the song throughout the day!

Play Games and Get Hands-On

Some students may pick up on the types of triangles through lectures or worksheets. Other students may need a more kinesthetic approach to help them learn to classify triangles. I’ve created several triangle hands-on activities and games that are perfect to use in the classroom for math centers, partner work, or just as a way to offer extra practice.

Triangle Board & Matching Games

You can never have too many board games in the classroom. Board games help students stay engaged with the concept they’re learning but also give them a bit of social skills practice as well. Partnering students with varying academic and social levels will allow them to learn from, coach, and support each other.

Here are a few of my favorite board games to help students practice classifying triangles.

Classify Triangles Math Board Game

This board game is a great way to slip in some extra practice and test students’ knowledge of triangles. Students take turns moving around the board to different triangle spaces. Everyone playing will identify the type of triangle on the board and then students compare their answers.

This game will prompt great conversations between students when they discuss their answers. Since all students answer each problem there are plenty of opportunities for them to provide supporting facts when their answers may differ from their peers’.

Triangles Matching Game

Another great way to test your students’ knowledge while giving them extra practice is this simple matching game. This game is great for individual practice or can be used with a partner or small group.

Students match names of different types of triangles with descriptions or pictures. Just like the board game, students can use this as an opportunity to provide their reasoning for choosing a specific answer. Peer discussion like this may even help some students better understand the concepts.

Classifying Quadrilaterals & Triangles Mobile

This activity can be used in so many ways and is a great way for students to get “hands-on” practice with shapes. Included in this resource are quadrilaterals and triangles, so it’s great to have on hand in any math classroom.

Students can either create mobiles, posters or simply use this resource as a sorting activity. You can also use the pages for interactive notebooks or study aids.

I hope you learned a new tip or two for teaching your students how to classify triangles.

It’s so important for students to have a solid understanding of the types of triangles before they move onto harder concepts, like perimeter and area of triangles. Providing lots of opportunities to practice and have fun, engaging activities like games and songs available will surely help them learn and retain all the information.

Do you have a special tip or trick to help students learn how to classify triangles? Share below in the comments!