Lesson 10

Calculating Slope

Lesson Narrative

Students extend their work with slope triangles to develop a method for finding the slope of any line given the coordinates of two points on the line. They practice finding slopes this way and use a graph in order to check their answer (especially the sign). 

Then students consider what information is sufficient to define (and accurately communicate) the position of a line in the coordinate plane. Lines with positive and negative slope are examined as students move flexibly between coordinates of points on a line, the slope of the line, and the graph showing the “uphill” or “downhill” orientation of the line. In order to communicate the location of the lines clearly, students engage in MP6. Many methods for describing the location of the lines are available, but students need to calculate carefully and use the coordinate grid in order to communicate the positions of the line clearly.


Learning Goals

Teacher Facing

  • Create a graph of a line using a verbal description of its features.
  • Describe (orally) the graph of a line using formal or informal language precisely enough to identify a unique line.
  • Generate a method to find slope values given two points on the line.

Student Facing

Let’s calculate slope from two points.

Required Preparation

Print and cut up slips from the Making Designs blackline master.  Prepare 1 copy for every 2 students.

Learning Targets

Student Facing

  • I can calculate positive and negative slopes given two points on the line.
  • I can describe a line precisely enough that another student can draw it.

CCSS Standards

Building On

Addressing

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