B5 Mathematics · Term 1 Week 7: Number Operations

Lesson notes

Learning Objectives

Indicator: B5.1.2.1.1 - Apply mental mathematics strategies and number properties, such as skip counting from a known fact, using doubling or halving, using patterns in the 9s facts, using repeated doubling or halving, to determine answers for basic multiplication facts to 81 and related division facts

By the end of the lesson, learners can:

Identify and name at least four mental mathematics strategies for solving basic multiplication facts to 81 and related division facts.
Skip count up or down from a known multiplication fact to find a new fact (e.g., using 5 × 7 = 35 to find 6 × 7 and 7 × 7).
Apply the doubling and halving strategies to solve multiplication and division facts they do not yet know by heart.
Use the patterns in the 9s facts (the “take away from 10 times” method) to multiply any single digit by 9 quickly.
Solve related division facts by thinking of the matching multiplication fact and explaining their reasoning.

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Curriculum details

Strand: Number (Strand 1)
Sub-strand: Number Operations (1.2)
Content standard: B5.1.2.1 - Describe and apply mental mathematics strategies and number properties to determine answers for basic multiplication facts to 81 and related division facts
Indicator: B5.1.2.1.1 - Apply mental mathematics strategies and number properties, such as skip counting from a known fact, using doubling or halving, using patterns in the 9sfacts, using repeated doubling or halving, to determine answers for basic multiplication facts to 81 and related division facts
Suggested placement: Term 1, Week 7 (Week 7 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. 65
Transcribed from the official NaCCA publication. Check this page against the source.

Exemplars (from the NaCCA curriculum)

E.g. 1 Describe the mental mathematics strategies used to determine a given basic fact, such as
- skip count up by one or two groups from a known fact (e.g., if 5 × 7 = 35, then 6 × 7 is equal to 35 + 7 and 7 × 7 is equal to 35 + 7 + 7)
- skip count down by one or two groups from a known fact (e.g., if 8 × 8 = 64, then 7 × 8 is equal to 64 - 8 and 6 × 8 is equal to 64 - 8 - 8)
- doubling (e.g., for 8 × 3 think 4 × 3 = 12, and 8 × 3 = 12 + 12)
- patterns when multiplying by 9 (e.g., for 9 × 6, think 10 × 6 = 60, and 60 - 6 = 54; for 7 × 9, think 7 × 10 = 70, and 70 - 7 = 63)
- repeated doubling (e.g., if 2 × 6 is equal to 12, then 4 × 6 is equal to 24 and 8 × 6 is equal to 48)
- repeated halving (e.g., for 60 ÷ 4, think 60 ÷ 2 = 30 and 30 ÷ 2 = 15)
- relating division to multiplication (e.g., for 64 ÷ 8, think 8 × … = 64)
E.g. 2 Recall multiplication facts to 81and related division facts