Lesson objective: Understand that numbers can be rounded to any place value.
Students bring prior knowledge of rounding based on place value from 3.NBT.A.1. This prior knowledge is extended to rounding to different place values. A conceptual challenge students may encounter is over relying on "rules" about rounding.
The concept is developed through work with a number line, which shows how the distance between actual numbers and rounded numbers can increase or decrease depending on the place value that numbers are rounded to.
This work helps students deepen their understanding of numbers because looking at number lines reveals the relationship between benchmark numbers, numbers half way between them, and where other numbers are located.
Students engage in Mathematical Practice 4 (model with mathematics) as they use number lines as a tool to determine the relative relationships between numbers.
Key vocabulary:
- benchmark
- exact
- hundreds
- midpoint
- number line
- round
- tens
- thousands
Special materials needed:
- colored pencils, if desired, for coloring on number lines
- graph paper, if desired, for creating number lines
