Placing the Protractor

• If working with a large group, utilize an overhead projector or Smart Board. Help students identify the outer scale, inner scale, zero-edge and center mark. Use these as vocabulary terms to assist in solidifying understanding. Inform students that the rule is the zero-edge is found at the same level as the 0 mark. Another rule is that the center mark is found at the middle of the zero-edge. The inner scale consists of the numbers on the inner edge of the protractor. The outer scale consists of the numbers on the outer edge of the protractor.
  
  

Measuring Angles

• Utilize examples from the textbook or retired state exams. When initially instructing the students, be explicit in illustrating mathematical concepts both verbally and visually. Ensure students first determine whether the angle is acute or obtuse. For an obtuse angle, students will utilize the top line. For acute angle, they will use the lower line. Next have students utilize protractors to place the center mark of the protractor on the point where the sides of the angle meet, also known as the vertex of the angle. Next have the students rotate the zero-edge of the protractor to line up with one line, also known as a ray, of the angle. Next the other line/ray of the angle should cross to the protractor’s scale. The next step is to take a reading of the angle measurement that crosses the scale of the protractor.
  
  

Avoiding Common Mistakes

• Encourage students to ensure they are focused on the correct scale, as a common mistake is to use the incorrect scale. Have students double check to ensure the center mark is on the vertex, the point of intersection, after rotating the protractor. Also have students count marks in the correct direction, paying close attention to numbers increasing or decreasing.
  
  

Tips

• Strive to make math real and meaningful. If possible, make some of the problems fun as students will be more open to learning and maintaining materials they enjoy. To check for understanding, have students write their own problems to solve or exchange. Coach their metacognition, thinking about their thinking, by having them explain their answers. If students have difficulty grasping concepts, allow them to work in small groups on assigned problems or problems they create. They can then present process, answer and explanation to the class. Have students write about math in order to solidify concepts. This will also allow you to observe their thought processes.