Algebraic Expressions Lesson 1 Episode 5 (Teachers)


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ET and Haleemah resolve a struggle from the previous episode and connect each part of their algebraic equation to its meaning in the swimming pool context.  

Episode Supports

Students’ Conceptual Challenges

Haleemah resolves her challenge from Episode 4 of making sense of 8 – 2 and x – 2 as a new quantity, namely as the number of tiles between two corners on one side of the pool [3:56 and 8:13].

Focus Questions

For use in a classroom, pause the video and ask these questions:

  1. [Pause the video at 3:54] In a previous lesson, Haleemah seemed to see the “minus two” as an action of taking the two corner tiles away from the side. How does she see the “minus two” now?
  2. [Pause the video at 7:59] How do you think ET and Haleemah will fix the  problem described by the teacher? Where do you think they will see that expression in their diagram?

Supporting Dialogue

  1. Ask students to consider the work of a (hypothetical) student, Keisha, who said the number of tiles in the border can be expressed as 4(x – 1) = B, where x is the number of tiles on one side of the border and B is the total number of tiles in the border. Have students draw and label a pool to show Keisha’s method. 
  2. Encourage students to reason quantitatively and abstractly by asking them to link symbols in the equation to parts of their diagram. For example, ask students to show what x – 1 means in their diagram in two different ways.