Using the Protractor

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Students will use their knowledge of acute, obtuse, and right angles to assist them in measuring angles with a protractor.

Big Idea

Protractors are useful tool that can be used for many situations.


10 minutes

Are you ready to challenge the dragons?  Radius will save us with his medallion! 

Radius is a character in the book Sir Cumference and the Great Knight of Angleland.  In this adventure of Sir Cumference his son Radius must travel to Angleland to battle the many dangers in order to gain his knighthood.  The author of this series does an amazing job incorporating academic vocabulary in a light-hearted, entertaining way. 

This book is a great way to start out this lesson because it highlights the content of this lesson very well.  There are lots of great moments to pause while reading this book to allow students to make observations.  The author and illustrator are very deliberate with everything they do.  It is important to stop and highlight those nuances in order to further student learning.



30 minutes


In a previous lesson(Around the Room) I had the students make an angle on a sticky note and then tour around the room to identify the angles their classmates had drawn.  This lesson is an extension to the tour activity in which students will now measure the angles on the sticky notes.  I have included a video of what this tour activity looks like in my room.   

Although using protractors is not specifically part of the 5th grade CCSS I think it is worth having students gain some familiarity with protractors.  The protractor becomes a vital part of geometry in 7th grade.  Also, I think there needs to be some relevance to talking about acute, obtuse, and right angles besides just saying there are three types of angles. 

Before the students begin the tour around the room I suggest doing a few examples on the document camera on how to use the protractor.  It is important to model for the students on how to line up the protractor with the vertex and the bottom line of the angle.  Also give some reminders about deciding which set of numbers to use on the protractor. 

I had the students use the same sticky note and notebook paper that they used in the previous lesson.  All of my students have math folders and were able to keep the papers in the folder.


10 minutes


After completing this activity I want to know what knowledge students have in using protractors.  A good way to monitor student learning is to have them put their thoughts into words.  I have the students do a quick write for their protractor knowledge.  Ask them think back the story of Radius in Angleland and pretend that Radius had no idea how to use the medallion/protractor.  Ask students to write a quick note to Radius to help him figure out what to do with the medallion.  By monitoring student responses I can gauge their level of understanding of protractors.