Lesson · Grade 6 · Mathematics
Five Types of Angles: Acute, Right, Obtuse, Straight and Reflex
- Grade 6
- Mathematics
- 1 min 21 s
- British Columbia
- BC6-MA-33
One arm turns from a fixed arm and stops at 40°, 90°, 130°, 180° and 250°, while a 0° to 360° bar fills in the range for each type. Each angle is named by comparing its size with 90° and 180°, and a check that 250° + 110° = 360° shows that a reflex angle is measured the long way round.
Concept: Types of angles: acute, right, obtuse, straight and reflex
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In one sentence
The question this lesson answers
How do we tell these five types of angle apart?
An angle measures the turn between two arms that meet at a point.
Transcript
What the lesson says
How do we tell these five types of angle apart?
An angle measures the turn between two arms that meet at a point.
We measure angles in degrees, and a full turn is 360 degrees.
Let us turn the arm and name the angle at five stops.
40 degrees is between 0 and 90 degrees, so this angle is acute.
At exactly 90 degrees, it is a right angle, marked with a small square.
130 degrees is between 90 and 180 degrees, so this angle is obtuse.
At exactly 180 degrees, the arms make a straight angle.
250 degrees is between 180 and 360 degrees, so this angle is reflex.
The other side is 110 degrees, and 250 plus 110 makes a full turn of 360 degrees.
From smallest to largest, these five types are acute, right, obtuse, straight and reflex.
To name an angle, compare its size with 90 and 180 degrees.
Curriculum
Where this fits
- British Columbia, Grade 6
Mathematics, Geometry and measurement: angle measurement and classificationBC6-MA-33
Previous: Area of a Trapezoid: Two Copies Make a ParallelogramNext: Measuring and Drawing Angles with a Protractor
The outcomes and strands follow the British Columbia curriculum.
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