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3-GM-2-5

Page history last edited by Tashe Harris 6 years, 2 months ago

3.GM.2.5 Using common benchmarks, estimate the lengths (customary and metric) of a variety of objects.

In a Nutshell

In second grade, students learn how the size of units affects the amount of units needed to measure an object. In third grade, students will learn the difference between customary and metric units when measuring. They then make estimations of length in centimeter, meters, inches, feet, and yards based on the object they are measuring.

Student Actions	Teacher Actions
Demonstrate a deep and flexible conceptual understanding when estimating the length of objects in both customary and metric units. Develop a productive mathematical disposition by justifying their estimation based on previous experiences with measuring objects. Make conjectures about the best estimation based on the explanations given from multiple peers. Communicate mathematically when comparing the estimation to the actual measurement and discuss the differences or similarities.	Pose purposeful questions to help students recall prior knowledge and justify their thinking. Questions may include: How can you justify your estimation? How are estimations helpful? How do you know when an estimation is inaccurate? How would you show your understanding of using estimation to find the length of an object? What approach would you use to find the estimated length of an….(object)? What unit of measurement would be best to find the estimated length of an object? Implement tasks where students must estimate the length of objects. Facilitate discussion within groups about the estimations presented.
Key Understandings	Misconceptions
Estimations are useful, but should not be used as a substitution to measurement in real life contexts. Estimations should be in smaller units when examining a smaller object and in bigger units when considering bigger objects. Understanding the length of a unit is essential (ex: they cannot estimate how many inches an object is if they do not understand the length of one inch).	Labeling units are unnecessary or unimportant. All estimations should be in the smallest unit or biggest unit. Estimations are more important than actual measurements.