# Lesson 6

Compare Methods for Subtraction

### Lesson Purpose

The purpose of this lesson is for students to compare methods for subtracting a one-digit number from a two-digit number with and without decomposing a ten.

### Lesson Narrative

In the first activity, students consider 3 methods for finding the difference represented using base-ten diagrams. In the second activity, students find the difference with and without decomposing a ten and represent their thinking using base-ten diagrams, words, or equations. Students are not expected to draw their work with base-ten diagrams in a specific way. Students should have access to base-ten blocks throughout the lesson and the cool-down. Students compare their methods, and the teacher records student thinking using base-ten diagrams and equations in the activity synthesis. In the lesson synthesis, students consider different ways to represent decomposing.

- Representation

### Learning Goals

Teacher Facing

- Describe how methods of subtraction are the same and different when subtracting a one-digit number from a two-digit number.

### Student Facing

- Let’s compare subtraction methods.

### Required Materials

Materials to Gather

Materials to Copy

- Target Numbers Stage 4 Recording Sheet

### Required Preparation

Activity 2:

- Remove 0 and 10 from each set of cards (or prompt students to remove them) before the activity.

### CCSS Standards

Addressing

### Lesson Timeline

Warm-up | 10 min |

Activity 1 | 15 min |

Activity 2 | 20 min |

Lesson Synthesis | 10 min |

Cool-down | 5 min |

### Teacher Reflection Questions

In upcoming lessons, students will subtract two-digit numbers from two-digit numbers with and without decomposing a ten. What do students need to understand about place value in order to use strategies that would require decomposing when subtracting by place?

### Suggested Centers

- Capture Squares (1–3), Stage 3: Add within 20 (Addressing)
- Five in a Row: Addition and Subtraction (1–2), Stage 6: Add within 100 with Composing (Addressing)

### Print Formatted Materials

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Student Task Statements | docx | |

Lesson Cover Page | docx | |

Cool Down | Log In | |

Teacher Guide | Log In | |

Teacher Presentation Materials | docx | |

Blackline Masters | zip |