Attacking Angles

I recently had a conversation with a 4th grade colleague. She had been measuring and drawing angles using a protractor with her student. The trouble was that no matter how much guided practice she provided, how many real life examples, how ever many ways she tried to attack angles, there was still a handful of students who were using the wrong numbers on the protractor. A 150 degree angle was recorded as 30 degrees and when drawing a 20 degree angle the student would draw a seriously obtuse illustration!

If this sounds familiar, and if you teach 4th or even 5th graders I’m sure it does, your students would likely benefit from vocabulary work along with some activities that will develop a sort of number sense around angles. So without any further ado, here are my strategies for Attacking Angles!

Strategy #1: Sort & Discuss Pictures
Students need to begin by developing a visual anchor for what an acute, right and obtuse angle looks like. Begin by talking about a 90 degree angle. Given a set of angles, students should look through and find the right angles. When students are confident, go ahead and relate right angles to acute as any angle which is more closed or smaller than a 90 degree angle. Given a set of angle pictures, have students sort through and find the acute angles. You may wish to stop right there and mix up all of your right and acute angles and ask a student to sort them. When they have developed confidence around these types of angles, you can repeat the activity with obtuse angles and sort the three.

Could this angle be 130 degrees? NO! Any kiddo with a
spatial understanding of angles would say so 🙂 

As students are sorting all 3 angle types, give them vocabulary to match the pictures.
“That’s an acute angle, it’s smaller than a right angle so it must be less than 90 degrees.”
“That’s an obtuse angle, it’s larger than a right angle so it must be more than 90 degrees.”
“I see you have an acute angle, could it possibly measure 120 degrees? Why or why not?”

Strategy #2: Sort & Discuss Angle Measures

What might 157 degrees look like? Could it be an acute angle?
No way!! 

Once students have a spatial understanding about angles, move into a sort that has NO pictures. By looking at a measure, a student should have a general idea about whether or not that measure is going to result in an acute, right or obtuse angle. Repeat a sort with only angle measures rather than pictures much in the same manner as you sorted and discussed the angle pictures.

Strategy #3: Synthesizing Our Learning. 

Let’s measure, this could be a 50 degree angle. 

Given a set of angle pictures and a set of angle measurements that match up, students can play a game of memory. The trick is that students should NOT measure every single set of cards they flip over, only the cards that they really need to measure. This is a way that you can synthesize the learning of the first two activities. For example, if a student flips a card reading 170 degrees and an acute angle, there is no reason they should need to get out their protractor, they know that these two cards can not possibly be a match.

No need to measure, this obtuse angle could NOT be 23 degrees! 

After completing these activities and having thorough understanding of the vocabulary terms acute, right and obtuse and the associated relationships to 90 degrees, students should no longer be making errors in reading the wrong numbers on a protractor because they will know when a measure doesn’t make sense. Likewise, they will know when a measure seems reasonable. 

Good luck attacking angles in your classroom!

If you are looking for a ready made resource to put these strategies into place, click on the cover below and head over to my store where these angle activities (along with additional task cards and word problems) can be found.

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