Lesson objective: Understand and represent multiplication equations as statements of comparison
Students bring prior knowledge of interpreting multiplication as an operation that uses a number of equal groups to show the total number of objects from 3.OA.1. This prior knowledge is extended to now interpreting multiplication as an operation to compare a product to its factors. A conceptual challenge students may encounter is distinguishing between additive and multiplicative comparison. For example, students will need to understand 3 more than 5 is different than 3 times as many as 5.
This concept is developed through tape diagrams and place value models, which help students, make sense of the comparison phrase, ___ times as many as ____, and represent verbal statements of multiplicative comparisons as multiplication equations.
This work prepares students to recognize the relationship between each place value as 10 times the value of the place to the right in subsequent lessons addressing 4.NBT.1.
Students engage in Mathematical Practice 1 (make sense of problems and persevere in solving them) as they draw diagrams and use place value charts to make sense of the comparative relationship between a product and its factors.
Key vocabulary:
- factor
- product
- comparison
Special materials needed:
- Place Value Discs (optional)
- Base Ten Units, Rods, and Flats (optional)