Number Operations · B6 Mathematics

Lesson notes

Learning Objectives

Indicator: B6.1.2.1.1 - Apply mental mathematics strategies and number properties, such as skip counting from a known fact, using doubling or halving, using patterns in the 9s and 11s 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:

State and describe at least three different mental mathematics strategies (skip counting, doubling, halving, patterns in 9s) used to find basic multiplication facts up to 81.
Apply skip counting up or down from a known fact to determine products for multiplication facts up to 81 (e.g., find 6 × 7 using the known fact 5 × 7 = 35).
Use doubling, repeated doubling, or repeated halving to find multiplication and division facts up to 81 (e.g., find 8 × 3 using 4 × 3 = 12, or find 60 ÷ 4 by halving twice).
Use the patterns in the 9s facts (such as subtracting from the 10s fact) to multiply any number from 1 to 9 by 9.
Relate division facts to corresponding multiplication facts to solve problems up to 81 (e.g., find 64 ÷ 8 by thinking of 8 × 8 = 64).

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Curriculum details

Strand: Number (Strand 1)
Sub-strand: Number Operations (1.2)
Content standard: B6.1.2.1 - Describe and apply mental mathematics strategies and number properties to determine answers for basic multiplication facts to 144 and related division facts
Indicator: B6.1.2.1.1 - Apply mental mathematics strategies and number properties, such as skip counting from a known fact, using doubling or halving, using patterns in the 9s and 11s facts, using repeated doubling or halving, to determine answers for basic multiplication facts to 81 and related division facts.
Suggested placement: Term 1, Week 8 (Week 8 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. 123
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