Grade 6 Angles & Triangles worksheet
from Gradelings · Name: ______________________
How to explain it
- Angles are measured in degrees. A right angle is 90°, a straight line is 180°.
- The three angles in any triangle add to 180°.
- Acute is under 90°. Obtuse is between 90° and 180°.
Example: A triangle has angles of 50° and 70°. What is the third angle? 50 + 70 = 120. 180 − 120 = 60. Answer: 60°
Question 1
Two angles of a triangle are 64° and 33°. What is the third angle?
answer box°
83 °
Hint: The three angles in any triangle add to 180°. Add the two you know, then subtract from 180°.
Question 2
This angle measures 180°. What kind of angle is it?
- right
- reflex
- straight
- obtuse
- acute
straight
Hint: Acute: less than 90°. Right: exactly 90°. Obtuse: between 90° and 180°. Straight: exactly 180°. Reflex: more than 180°.
Question 3
An isosceles triangle has two equal base angles. Its third angle is 22°. What is each base angle?
answer box°
79 °
Hint: Subtract the third angle from 180°. The two equal base angles share what is left, so divide by 2.
Question 4
Can a triangle have two obtuse angles?
- Yes, in a scalene triangle
- No, two obtuse angles add to more than 180°
- Only in a right triangle
- Yes, if the sides are long
No, two obtuse angles add to more than 180°
Hint: Obtuse angles are more than 90° each. Two of them already go past the 180° total.
Question 5
About how many degrees is this angle?
- 345°
- 255°
- 135°
- 210°
210°
Hint: Compare with benchmarks: a square corner is 90°, a straight line is 180°, and three quarters of a full turn is 270°.
Question 6
A triangle has sides of 11 cm, 8 cm and 12 cm. What type of triangle is it?
- isosceles
- equilateral
- scalene
scalene
Hint: Classify by sides. Equilateral: all 3 sides equal. Isosceles: 2 sides equal. Scalene: no sides equal.
Question 7
Two angles together make a straight line. One of them is 142°. What is the other angle?
answer box°
38 °
Hint: Angles that make a straight line add to 180°. Subtract the angle you know from 180°.
Question 8
A triangle has angles of 54°, 90° and 36°. Classify it by its angles.
- acute triangle
- right triangle
- obtuse triangle
right triangle
Hint: Acute: all angles less than 90°. Right: one angle is exactly 90°. Obtuse: one angle is more than 90°.
Question 9
Two angles together make a straight line. One of them is 40°. What is the other angle?
answer box°
140 °
Hint: Angles that make a straight line add to 180°. Subtract the angle you know from 180°.
Question 10
Two angles of a triangle are 15° and 85°. What is the third angle?
answer box°
80 °
Hint: The three angles in any triangle add to 180°. Add the two you know, then subtract from 180°.
Answer key
- 1. 83 °
- 2. straight
- 3. 79 °
- 4. No, two obtuse angles add to more than 180°
- 5. 210°
- 6. scalene
- 7. 38 °
- 8. right triangle
- 9. 140 °
- 10. 80 °
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