Year 6 Maths: Triangles and Type

Introduction to Triangles

Hello, Year 6! Today, we’re going to learn about triangles. Triangles are shapes that have three sides and three angles. They can look different depending on their sides and angles. Let’s explore the different types of triangles together!

Types of Triangles

1. By Sides

Triangles can be classified based on the length of their sides:

• Equilateral Triangle
  • All three sides are the same length.
  • All three angles are 60 degrees.
• Isosceles Triangle
  • Two sides are the same length, and one side is different.
  • The angles opposite the equal sides are the same.
• Scalene Triangle
  • All three sides are different lengths.
  • All three angles are different.

2. By Angles

Triangles can also be classified based on their angles:

• Acute Triangle
  • All three angles are less than 90 degrees.
• Right Triangle
  • One angle is exactly 90 degrees (a right angle).
• Obtuse Triangle
  • One angle is greater than 90 degrees.

Key Rules About Triangles

1. The sum of the angles in any triangle is always 180 degrees.
   • For example, if one angle is 50 degrees and another is 60 degrees, the third angle must be 70 degrees because $$50 + 60 + 70 = 180$$ .
2. In an equilateral triangle, if one angle is 60 degrees, all angles are 60 degrees.
3. In an isosceles triangle, if you know the length of one side and the angle opposite it, you can find the other angles.

Tips and Tricks

• Remember the different types of triangles based on sides and angles.
• Use a ruler to measure the sides of a triangle to check if they are equal.
• Use a protractor to measure the angles to see if they add up to 180 degrees.

Questions

Easy Level Questions

1. What do you call a triangle with all sides the same length?
2. How many angles does a triangle have?
3. What is the sum of the angles in a triangle?
4. What type of triangle has one right angle?
5. Draw an equilateral triangle.
6. What do we call a triangle with no equal sides?
7. What angle measurement makes a triangle a right triangle?
8. If two sides of a triangle are 5 cm and 5 cm, what type of triangle is it?
9. Can a triangle have two right angles? (Yes/No)
10. What do you call a triangle with one angle greater than 90 degrees?

Medium Level Questions

11. If one angle of a triangle is 30 degrees and another is 70 degrees, what is the third angle?
12. Draw an isosceles triangle and label its equal sides.
13. Can an isosceles triangle also be a right triangle? (Yes/No)
14. How many equal angles does an equilateral triangle have?
15. If a triangle has angles of 40 degrees and 60 degrees, what type of triangle is it?
16. What is the measurement of each angle in an equilateral triangle?
17. If a triangle has sides of lengths 3 cm, 4 cm, and 5 cm, what type of triangle is it?
18. How can you tell if a triangle is scalene?
19. Draw a right triangle and label the right angle.
20. What type of triangle has two sides that are equal and one angle that is 100 degrees?

Hard Level Questions

21. A triangle has two angles measuring 45 degrees. What is the type of triangle?
22. In a triangle, if one angle measures 120 degrees, what can you say about the other two angles?
23. If a triangle is isosceles and one angle is 80 degrees, what are the other two angles?
24. Can a triangle exist with sides of lengths 2 cm, 2 cm, and 5 cm? (Yes/No)
25. Calculate the third angle in a triangle where the other two angles are 55 degrees and 85 degrees.
26. Draw a triangle with angles measuring 30 degrees, 40 degrees, and 110 degrees. What type is it?
27. If you know two sides of a triangle are 6 cm and 8 cm, what could the length of the third side be?
28. How would you classify a triangle with angles of 90 degrees, 30 degrees, and 60 degrees?
29. Construct a triangle with sides of lengths 7 cm, 8 cm, and 9 cm. What type of triangle is it?
30. Explain why the sum of the interior angles of any triangle is always 180 degrees.

Answers

Easy Level Answers

1. Equilateral Triangle
2. Three angles
3. 180 degrees
4. Right Triangle
5. (A drawing of an equilateral triangle)
6. Scalene Triangle
7. 90 degrees
8. Isosceles Triangle
9. No
10. Obtuse Triangle

Medium Level Answers

11. 80 degrees
12. (A drawing of an isosceles triangle)
13. Yes
14. Three equal angles
15. Acute Triangle
16. 60 degrees
17. Scalene Triangle
18. All sides are different lengths.
19. (A drawing of a right triangle)
20. Isosceles Triangle

Hard Level Answers

21. Right Triangle
22. The other two angles must add up to 60 degrees, making them acute.
23. Each of the other two angles would be 50 degrees.
24. No
25. 40 degrees
26. Obtuse Triangle
27. It could be between 2 cm and 14 cm.
28. Right Triangle
29. Scalene Triangle
30. Because each angle contributes to the total, and they must fit together to form a triangle.

Now you have learned about triangles and their types! Practice these questions to test your knowledge!