B5 Mathematics · Term 1 Week 9: Number Operations

Lesson notes

Learning Objectives

Indicator: B5.1.2.2.1 - Multiply multi digit numbers by 2-digit numbers efficiently

By the end of the lesson, learners can:

Multiply a 2-digit number by a 2-digit number using the expand and box (partial decomposition) method, showing each partial product clearly.
Multiply a 2-digit number by a 2-digit number using the column (vertical) method, carrying correctly where necessary.
Multiply a 2-digit number by a 2-digit number using the distributive property, such as 25 × 32 = (25 × 30) + (25 × 2).
Multiply a 2-digit number by a 2-digit number using the lattice method, drawing the correct grid and reading the final answer correctly.
Solve a word problem that requires multiplying a 2-digit number by a 2-digit number in a real-life situation, explaining the reasoning used.

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Curriculum details

Strand: Number (Strand 1)
Sub-strand: Number Operations (1.2)
Content standard: B5.1.2.2 - Demonstrate an understanding of multiplication of a 2 or 3-digit number by a 2 or 3-digit number.
Indicator: B5.1.2.2.1 - Multiply multi digit numbers by 2-digit numbers efficiently
Suggested placement: Term 1, Week 9 (Week 9 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: Mathematics Curriculum for Primary Schools (Basic 4-6), 2019, p. 67
Transcribed from the official NaCCA publication. Check this page against the source.

Exemplars (from the NaCCA curriculum)

E.g. 1. Multiplication of whole numbers using the "expand and box" method (partial decomposition method). Lead learners to multiply a 3-digit number by a 1-digit number as shown below, for example 448 × 2 =? × 400 40 8
2 800 80 16
448 × 2 = (400 × 2) + (40 × 2) + (8 × 2) = 800 + 80 + 16 = 800 + 80 + (10 + 6) = 800 + 90 + 6 = 896

Figure from the b5 mathematics curriculum, printed page 67

E.g. 2. Multiplication of whole numbers using the Column or vertical method; i.e. 25×32
E.g. 3. Multiplication of whole numbers using the Distributive property; i.e. 25×32

E.g. 4. Multiplication of whole numbers using the lattice method. Have learners draw a 2 by 1 rectangular box for solving 54 × 3.
E.g. 5. Have learners draw a 2 by 2 rectangular box for solving 79×58.

Figure from the b5 mathematics curriculum, printed page 68