Your device is currently offline. You can view downloaded files in My Downloads.

Lesson Plan

4. Use rounding to determine if a sum or difference is reasonable (C)

teaches Common Core State Standards 3.2C
teaches Common Core State Standards 3.NS.9
teaches Common Core State Standards CCSS.Math.Content.3.NBT.A.1
teaches Common Core State Standards CCSS.Math.Practice.MP8
teaches Common Core State Standards MAFS.3.NBT.1.1
teaches Common Core State Standards 4.2D
Quick assign

You have saved this lesson!

Here's where you can access your saved items.


Card of

or to view additional materials

You'll gain access to interventions, extensions, task implementation guides, and more for this lesson.

Lesson objective: Extend understanding of estimation to determine reasonability of sums and differences in real-world contexts.

Students have prior knowledge of estimation from 3.NBT.A.1. This prior knowledge is extended to addition and subtraction as students determine the reasonability of an estimated sum or difference. A conceptual challenge students may encounter is that rounding values will not always result in a reasonable estimate. 

The concept is developed through work with a number line, which supports understanding of estimation as using close, benchmark numbers.

This work helps students deepen their understanding of number because students compare estimated sums to actual sums and determine which solution makes sense in the given scenario.

Students engage in Mathematical Practice 8 (Look for and express regularity in repeated reasoning) as they use their knowledge of rounding and apply it to a new situation. They determine estimates and reasonability of calculations with sums and differences.

Key vocabulary:

  • estimate
  • front-end estimation
  • overestimate
  • reasonable
Related content

Appears in

Developing strategies for addition and subtraction

Provide feedback