Lesson Plans for Grade Five: Classifying Angles

Teaching Fifth Graders about Classifications of Angles

The basic angles that you'll probably discuss with your fifth graders are right, acute and obtuse angles. You also might cover straight angles. Less frequently, you'll be expected to explain reflex or complete angles. There are some fun games to play once your students know the names and can classify angles.

Introducing Angles

Tell your students that as an angle gets bigger, the name changes. As you draw or otherwise demonstrate the angles, introduce the terms ray or arm and vertex. Draw the curved line that shows the degree of arc that determines the classification of the angle. Later you can point out that two lines make two angles at the same time - one 'inside' the lines and one 'outside' of them. This is also a good time to introduce protractors and show your students how angles relate to numbers on the protractor.

Demonstrate angles by drawing them on the board or demonstrate with the hands of a clock. Measure these angles with a protractor. To add a hands-on element, give each child two toothpicks or straws so they can make angles as you demonstrate them. Give your students some paper and crayons or colored pencils to draw angles. Present angles in ways that can help students remember the names.

Straight Angle - 180 Degrees

Kids are already familiar with straight lines. Tell them that a straight angle is the same as a straight line, and draw the curved line to show them the degree of arc.

Acute Angle - < 90 Degrees

Draw an acute angle and explain its size. Add some fluff to it and turn it into a rabbit, or dog or whatever 'cute' object you want. Then ask the class, 'Isn't this a-cute little angle?' Let them draw their version of 'a-cute' little angle.

Right Angle - 90 Degrees

Show your students some obvious right angles - the corner of a paper, a book or a desk. Then have the children each show you another right angle in the room. Each time they do this, respond with, 'That's right, a right angle.'

Obtuse Angle - > 90 Degrees But < 180 Degrees

Dr. Seuss is of great help here because his name rhymes with obtuse. Make up a Dr. Seuss-type rhyme, such as 'My cat is on the loose, my fish is in the juice and this angle is obtuse.' Your students can create their own Dr. Seuss rhymes for the obtuse angle.

Reflex Angle - > 180 Degrees But < 360 Degrees

Have the children look down at their knees while they're sitting at their desks. The 'outside angle' of a bent knee is a reflex angle. Have them tap their knees to test their reflexes, just as a doctor does, to help them remember the name.

Complete Angle - 360 Degrees

At first, this angle looks like a straight angle. However, show them that the vertex of a straight angle is somewhere along the line, whereas the vertex of a complete angle is at an end of the line. Explain to your students that, 'This angle goes completely around the line, so it's a complete angle.'

Angle Games to Reinforce Learning

You can tie math lessons to other subjects in the curriculum to help reinforce the practical value of the concepts. Try some of these fun activities.

Angles in Gym Class

Call out the name of an angle and have the children try to make one with their hands, arms or whole bodies. Give kudos for the most original display of the angle.

Story Angles

You did this when they made-up Dr. Seuss rhymes. Suggest that your students write a story in which the characters are the various kinds of angles. Each angle character can do things relevant to their classification. They can print their names and identify all of the kinds of angles represented.

Alligators from Angles

Just as you did with the acute angle, you can ask your students to draw the angle you name and turn it into a picture, making sure they're able to clearly see the lines of the angle. For example, have them draw an alligator or a house that has each of the angles prominently illustrated in the picture.