Lesson plan

# 9. Three-digit subtraction with regrouping (FP)

teaches Common Core State Standards MP8 http://corestandards.org/Math/Practice/MP8
teaches Common Core State Standards MP1 http://corestandards.org/Math/Practice/MP1
teaches Common Core State Standards 2.NBT.B.9 http://corestandards.org/Math/Content/2/NBT/B/9
teaches Common Core State Standards 2.NBT.B.7 http://corestandards.org/Math/Content/2/NBT/B/7

# 9. Three-digit subtraction with regrouping (FP)

Lesson objective: Subtract two three-digit numbers involving regrouping using place value strategies and the relationship between addition and subtraction.

This lesson helps to build fluency with whole number three-digit subtraction with regrouping. Tape diagrams, base ten blocks, and number lines are used here because they support students' use of multiple strategies related to place value and properties of operations. This work develops students' understanding that subtraction regrouping strategies used with two-digit numbers can be used with three-digit numbers.

Students engage in Mathematical Practice 8 (Look for and express regularity in repeated reasoning) as they apply regrouping strategies from two-digit subtraction to three-digit subtraction, using base ten blocks and number lines as tools to support multiple strategies.

Key vocabulary:

• base ten blocks
• decompose
• digit
• equivalent
• hundreds
• number line
• ones
• place value
• regroup
• tape diagram
• tens

Special materials needed:

• Number cube (1 per pair of students)