Lesson 10

Classifying Shapes

Est. Class Sessions: 2–3

Daily Practice and Problems

Teacher Notes
X

TIMS Task

    1. 60°
    2. 120°
    3. 25°
  2. Possible response: First, I found that angle ADB was equal to 60°. When you add the 3 angles in a triangle they equal 180°, so 90° + 30° = 120° and 180° − 120° = 60°. Then I knew that the sum of angle ADB and angle BDC will equal 180°, so 180° − 60° = 120°.

Ongoing Assessment

Use DPP item BB to assess students' abilities to use addition and subtraction to find unknown angle measures [E1].

The Workshop in Lesson 6 provides targeted practice.

BB. Angle Measures

  1. Use the drawing below to find the measurement of each angle without using a protractor.
    1. ∠ADB
    2. ∠BDC
    3. ∠CBD
  2. Show or tell how you found the answer for 1B.