Strategies for Decomposing Tens and Hundreds

Description

Topic E begins with an extension of mental math strategies learned in first grade, when students learned to subtract from the ten by using number bonds. In Lesson 23, they return to this strategy to break apart three-digit minuends and subtract from the hundred.

In Lesson 24, students use place value disks on a place value chart to represent subtraction and develop an understanding of decomposition of tens and hundreds.

In Lesson 25, students move toward the abstract when they model decompositions on their place value charts while simultaneously recording the changes in the vertical form.

Students use math drawings in Lesson 26 as they move away from concrete representations and into the pictorial stage.

Topic E closes with the special case of subtracting from 200.