This activity revisits the idea of decomposing a unit in one place into 10 units of the place value to its right when subtracting multi-digit numbers using the standard algorithm. Students recall how this is done as they subtract numbers in which decomposition is necessary.
To support students with understanding the context, the activity Launch introduces a saree (traditional wedding attire for women in India) and the idea of family heirlooms, or gifts passed down from generation to generation.
When students create a subtraction problem that does not require decomposition of a unit when using the standard algorithm, they make use of structure and their understanding of subtraction as they choose the digits for the numbers in their difference (MP7).
This activity uses MLR7 Compare and Connect. Advances: representing, conversing
Representation: Develop Language and Symbols. Activate or supply background knowledge. To help students recall the term decompose, represent a four-digit number (for example, 2,467) with both base-ten blocks and digits in a place value chart. Ask, “what does it mean to decompose a unit?” Show an example of decomposition, such as exchanging one long rectangle for ten small cubes. Notate this in the place value chart by crossing out the 6 and 7, and writing 5 and 17 above them. Reset the place value blocks and show additional examples as needed.
Supports accessibility for: Conceptual Processing, Memory, Language
