# Lesson 5

Standard Algorithm: Multi-digit Numbers without Composing

### Lesson Purpose

The purpose of this lesson is for students to use the standard algorithm to multiply up to three-digit numbers and two-digit numbers without composing a new unit.

### Lesson Narrative

In a previous lesson, students used the standard algorithm to multiply up to five-digit numbers by one-digit numbers. They connected the standard algorithm to a different algorithm that uses partial products. In this lesson, students find products of a three-digit number and a two-digit number when composing is not required. The numbers in this lesson do not require composing so that students can make sense of where to record the second partial when using the standard algorithm to multiply a three-digit number by a two-digit number. Students will work with products of a two-digit number and a three-digit number when composing is required in the next lesson.

- Representation

- MLR8

### Learning Goals

Teacher Facing

- Use the standard algorithm to multiply up to three-digit numbers and two-digit numbers, without composing new units.

### Student Facing

- Let’s use the standard algorithm to multiply two-digit numbers and three-digit numbers.

### Required Preparation

### Lesson Timeline

Warm-up | 10 min |

Activity 1 | 20 min |

Activity 2 | 15 min |

Lesson Synthesis | 10 min |

Cool-down | 5 min |

### Teacher Reflection Questions

How did the student work that you selected impact the direction of the discussion? What student work might you pick next time if you taught the lesson again?

### Suggested Centers

- Number Puzzles: Multiplication and Division (4–5), Stage 2: Multi-digit Factors (Addressing)