Develop Rules for Multiplying Signed Numbers

Investigate the case of two negatives make a positive. Pupils fill in a quadrant system to generate the products of integers. They analyze the quadrants to find patterns and relationships to help complete the table values. The teacher leads the class in a algebraic proof to verify the patterns were correct. 

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CCSS: Designed
Additional Tags
Instructional Ideas
  • Emphasize the concept of giving away to represent a negative quantity
  • Use a number line on the floor and have class members hop a given number of times a length to show multiplication
Classroom Considerations
  • The class should understand the relationship between the signs of ordered pairs and the reflections across axes
  • The lesson is installment 11 in a series of 25
Pros
  • Uses two different approaches to arrive at the sign of the products
  • Includes suggestions for visuals to place in the classroom
Cons
  • Wording of the first lesson outcome makes it sound like absolute value can be negative
  • The answer key for the problem set has some formatting issues that make it difficult to read
Common Core