Number Operations · JHS1 Mathematics

Lesson notes

Learning Objectives

Indicator: B7.1.2.1.2 - Apply mental mathematics strategies and number properties used to perform calculations.

By the end of the lesson, learners can:

Use the halving and doubling technique to multiply pairs of numbers mentally, such as 28 × 5 and 36 × 25.
Apply the distributive property to break apart numbers into friendlier parts and multiply, such as 7 × 15 and 18 × 6.
Justify their choice of strategy when solving a multiplication problem, explaining why one strategy is more efficient than another.
Solve multiplication problems accurately using at least two different mental mathematics strategies and check that their answers agree.

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Curriculum details

Strand: Number (Strand 1)
Sub-strand: Number Operations (1.2)
Content standard: B7.1.2.1 - Apply mental mathematics strategies and number properties used to solve problems
Indicator: B7.1.2.1.2 - Apply mental mathematics strategies and number properties used to perform calculations.
Suggested placement: Term 1, Week 3 (Week 3 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, Common Core Programme (JHS1-JHS3), 2023, p. 7
Transcribed from the official NaCCA publication. Check this page against the source.

Exemplars (from the NaCCA curriculum)

E.g. 1. Apply the halving and doubling techniques to determine the product of two given numbers.
i. 28 x 5, think 14 x 10=140
ii. 125 x 4, think (125 x 2) x 2 = 250 x 2 = 500
E.g. 2. Apply the distributive property to determine the product of two given numbers
i. 7 x 15, think 7 × (10 + 5) = 70 + 35 = 105
ii. 18 × 6, think (20 - 2) × 6 = (20 × 6)-(6 × 2) = 120 -12 = 108