Grade 4 Geometry: Understanding Angles

Worked examples

Real problems from the practice worksheets, solved one step at a time.

1. Example 1

   An angle measures 180°. What type of angle is it?

   1. Compare the angle with a right angle (90°, a square corner) and a straight angle (180°, a straight line).
   2. 180° makes a straight line.
   3. An angle of exactly 180° is a straight angle.

   Answer: straight

2. Example 2

   An angle measures 132°. What type of angle is it?

   1. Compare the angle with a right angle (90°, a square corner) and a straight angle (180°, a straight line).
   2. 132° is more than 90° but less than 180°.
   3. An angle between a right angle and a straight angle is an obtuse angle, so 132° is obtuse.

   Answer: obtuse

3. Example 3

   An angle measures 18°. What type of angle is it?

   1. Compare the angle with a right angle (90°, a square corner) and a straight angle (180°, a straight line).
   2. 18° is less than 90°.
   3. An angle smaller than a right angle is an acute angle, so 18° is acute.

   Answer: acute