Lesson plan



|Math Lesson: Measuring Angles |Grade Level: 4-5 |

|Lesson Summary: The teacher will pre-assess students’ knowledge of the terms acute angle, right angle, obtuse angle, and straight angle by showing students |

|pictures of angles and having them classify each angle. Students will then learn how to use a protractor to draw some benchmark angles: 45°, 90°, and 180°. |

|Students will work in pairs to place other angles by size in comparison to each benchmark angle. They will then use protractors to check their work. Independently,|

|on-level learners will solve multiple choice questions about the reasonableness of angle measurements and measure given angles using a protractor. Advanced |

|learners will look at a picture of a house with labeled angles. They will sort the labeled angles according to type: acute, obtuse, or right. They will also choose|

|4 of the labeled angles to measure with a protractor. Struggling learners will order number cards from 10° to 170° and order pictures of the same angles from least|

|to greatest, matching the picture with the number of degrees. They will also practice using the protractor to make sure each angle matches the given measurement. |

|Lesson Understandings: |

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|The students will know… |

|That protractors measure angles. |

|How to use a protractor to measure angles. |

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|The students will be able to… |

|Use a protractor to measure angles. |

|Learning Styles Targeted: |

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|Visual |

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|Auditory |

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|Kinesthetic/Tactile |

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|Pre-Assessment: Tell students that today they are going to learn how to measure different kinds of angles, but first you want to know that they understand how to |

|classify different angles according to type. Project a copy of the Pre-Assessment*, and explain to students that you are going to ask them some questions about the|

|pictures of the angles. They should hold up the number of fingers that corresponds to the type of angle they see pictured. Make sure students understand to hold up|

|1 finger if they think the angle is a straight angle, 2 fingers if they think the angle is an obtuse angle, 3 fingers if they think the angle is a right angle, and|

|4 fingers if they think the angle is an acute angle. Point to picture A, and have students hold up the number of fingers that corresponds to their answer. Repeat |

|for the remaining pictures. The answers for the pictures are: |

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|A- 4 (acute) |

|B- 1 (straight) |

|C- 3 (right) |

|D- 2 (obtuse) |

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|If you see that students are struggling, stop and review the 4 terms with students. |

|Whole-Class Instruction |

|Materials Needed: writing utensils, 1 protractor per student, 3 index cards per pair of students, 1 set of pre-cut Sorting Pictures* per pair of students, 1 copy |

|of the Independent Practice* per student |

|Procedure: |

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|Because they already know how to classify angles into acute, right, obtuse, and straight, tell students that today they are going to learn how to measure angles. |

|Point out that mathematicians use lots of different instruments to measure: clocks to measure time, thermometers to measure temperature, rulers to measure length, |

|scales to measure weight, and so on. Students will learn how to use protractors to measure angles. Hold up a protractor for students to see. |

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|Tell students that they are first going to learn some benchmark angles to use as comparisons. The benchmark angles are very common angles that students need to |

|become familiar with. Put students into pairs, and give each pair a protractor and 3 index cards. Have students write 45° on one card, 90° on one card, and 180° on|

|the last card. Place 3 index cards under a document camera that you have labeled in the same way. Model for students how to use a protractor to draw a 45° angle on|

|the 45° card. Have students do the same. As students are drawing, monitor that they are using the protractor correctly. Ask students what kind of angle is the 45° |

|angle. Elicit responses until a student says, “acute.” Tell students that the definition of acute angle is an angle that is smaller than 90°. |

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|Tell students that 45 is half of 90, so a 90° angle is like two 45° angles stacked together. Use the 90° card to model for students how to use the protractor to |

|draw a 90° angle. Tell students that they should draw a 90° angle on the corresponding index card. Remind them that both partners need to practice using the |

|protractor. Ask students what kind of angle they have drawn. Elicit responses until a student says, “right.” Tell students that the definition of a right angle is |

|an angle that measures exactly 90°. |

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|Point out to students that 90 + 90 = 180, so a 180° angle is like putting two right angles back to back. Use the protractor to model how to draw a 180° angle on |

|the corresponding index card. Students should do the same on their index cards. Monitor that they are doing this correctly. |

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|Ask students to place their 3 index cards on their desks in order from the smallest angle to the largest angle. Tell students to leave some space in between each |

|card because they will be placing some new angle cards in between each benchmark angle. Monitor that students have placed the cards in the order 45°, 90°, 180°. |

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|Give each pair of students a set of pre-cut Sorting Pictures. Tell students that you want them to look at each picture and compare it to the benchmark angles. Have|

|them look at angle A. Ask students if they think it is smaller than the 45° picture. Elicit responses until a student says no. Tell students this means that the |

|angle must be larger than 45°. Ask students if angle A is larger than 90°. Elicit responses until a student says no. Tell students this means that means the angle |

|must be between 45° and 90°. Have students place angle A in between the 45° and 90° cards. Tell students that you want them to look at the other angle cards and, |

|using a process of elimination, place them where they think they should go in relation to the benchmark angles. |

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|Allow students to work in with their partners, monitoring that they are placing the cards correctly. The cards should be placed as follows: |

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|Smaller than 45° - C and E |

|Between 45° and 90° - A and D |

|Between 90° and 180° - B and F |

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|Once you see that all pairs have placed the angles correctly, walk students through using the protractor to measure each angle, checking to make sure the |

|measurement fits in the category where it was placed. You may want to accept angle measurements within 1-2 degrees of the actual measurement. The angles should |

|measure as follows: |

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|A - 80° |

|B - 125° |

|C – 19° or 20° |

|D – 64 or 65° |

|E - 36° |

|F - 100° |

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|Give each student his/her own protractor and a copy of the Independent Practice. Make sure students understand the directions, and allow them to work |

|independently. Again, you may want to accept answers within 1-2 degrees of the measurements on the answer key. |

|Advanced Learner |

|Materials Needed: 1 copy of the Advanced Learner Problem* per student, writing utensils, 1 protractor per student |

|Procedure: |

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|Give each advanced learner a copy of the Advanced Learner Problem and a protractor. Read aloud the directions to students, check for understanding, and allow them |

|to work independently. |

|Struggling Learner |

|Materials Needed: 1 set of pre-cut Struggling Learner Cards* per pair of students, 1 protractor per pair of students |

|Procedure: |

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|Put students into pairs, and give each pair a set of pre-cut Struggling Learner Cards. Tell students that in their set of cards, there are angles cards from 10° |

|up to 170° in multiples of ten. Have students order the number cards from least to greatest. |

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|After students have correctly ordered their cards, tell them that the rest of the cards are pictures of each of those angles. Have students use their hands to make|

|a small acute angle, like a barely open alligator’s mouth. Tell students that an angle so small has a small measurement. Have students open their hands a bit wider|

|and tell them that as their hands grow further apart, the measurement of the angle also gets larger. Have students practice opening their hands wider and wider, |

|emphasizing that the measurement is growing as they open their hands. |

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|Now tell students that you want them to look at the pictures of the angles on the rest of the cards and work together with their partners to put the pictures in |

|order of smallest to largest. Allow students a few moments to work together to order the cards. Monitor that they are using reasoning to put the pictures in order.|

|If students make a few mistakes, that is ok. They will have the chance to change them soon. |

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|Once all pairs have ordered their pictures, tell them to match the smallest measurement card with the smallest angle cards and so on until all pictures have a |

|matching measurement. Review with students how to use a protractor, and give each pair their own to use. Tell students that you want them to use the protractor to |

|measure each angle to make sure they matched the picture correctly with the angle measurement. Tell students that if they found a mistake, they should rearrange |

|their cards to show the correction. While students are working, monitor closely that they are using the protractor correctly to check each angle’s measurement. |

*see supplemental resources

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