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## 4th grade

### Course: 4th grade > Unit 11

Lesson 4: Classifying triangles# Types of triangles review

Review ways to classify triangles based on their sides lengths and angles. Practice classifying triangles.

## Classifying triangles by their angles

### Acute triangles

An ${\text{acute}}$ triangle has ${\text{3 angles that}}$ ${\text{each measure less than}{90}^{\circ}}$ . Below are examples of ${\text{acute triangles}}$ .

### Right triangles

A ${\text{right}}$ triangle has ${\text{1 angle that measures}{90}^{\circ}}$ and $2$ acute angles. Below are examples of ${\text{right triangles}}$ .

### Obtuse triangles

An ${\text{obtuse}}$ triangle has ${\text{one angle that measures}}$ ${\text{more than}{90}^{\circ}}$ and $2$ acute angles. Below are examples of ${\text{obtuse triangles}}$ .

*Want to learn more about classifying triangles? Check out this video.*

*Want to try more problems like this? Check out this exercise*

## Classifying triangles by their side lengths

### Equilateral triangles

An ${\text{equilateral}}$ triangle has ${\text{three equal sides}}$ . Below are examples of ${\text{equilateral}}$ triangles.

### Isosceles triangles

An ${\text{isosceles}}$ triangle has ${\underset{\u2015}{\text{at least}}}$ ${\text{two equal sides}}$ . Below are examples of ${\text{isosceles}}$ triangles.

### Scalene triangles

A ${\text{scalene}}$ triangle has ${\text{no equal sides}}$ . Below are examples of ${\text{scalene}}$ triangles.

*Want to try more problems like this? Check out this exercise.*

## Want to join the conversation?

- Why can't I go back to selecting? I got a wrong and I can't go back(69 votes)
- It just won't let you.(12 votes)

- why is the isosceles triangle and the equilateral both classified as each other(43 votes)
- because an equilateral triangle is all equill sides and an isosceles triangle is two or more equill sides(17 votes)

- Is their any more triangle practices?(21 votes)
- No. You will have to do them over if you want extra practice.(11 votes)

- Why are triangles used in math?(14 votes)
- it is because it uses geometry(6 votes)

- I don’t understand why an equilateral triangle is constantly being defined as and Isosceles triangle.(9 votes)
- An equilateral triangle has 3 equal length sides. An isosceles triangle has at least 2 sides of the same length. Thus all equilateral triangles are also isosceles.(25 votes)

- if all of the angels are acute but lenghths are different what is that?(6 votes)
- um whenever i double tap a question it ameatiatily says its wrong(11 votes)
- dont double tap just tap and check(8 votes)

- I'm starting sixth grade next year, and I'm already at unit 4 lesson 2. I started doing it this summer for hobby work, because I wanted to be an architect, but I had not studied geometry so I went ahead to study ALL the geometry. Does anyone think I overdid it?(11 votes)
- As long as you can understand what you are studying, you can go as far as you want to go.(9 votes)

- i got my one right but it said i got it worng(11 votes)
- I... I think that means you got it wrong, but you don't understand. You might want to check your answer or ask someone else to explain it to you.(2 votes)

- this was so easy ;-; >:((5 votes)
- ITS NOT IF YOUR ON AN IPAD! Sorry but you must drag the lines together and it’s really frustrating.(14 votes)