Number Operations (Addition… · B2 Mathematics

Lesson notes

Learning Objectives

Indicator: B2.1.2.3.1 - Use mental strategies for basic addition facts to 19 and related subtraction facts to 19

By the end of the lesson, learners can:

Quickly state the number that is 1, 2, 5, or 10 more or less than any number between 1 and 100.
Identify and state the double of any number between 1 and 12 without writing it down.
Use at least two mental strategies (counting up, making doubles, making 10s) to solve addition facts to 19 within 3 seconds.
Use counting down and “think addition” strategies to solve subtraction facts to 19 within 3 seconds.
Explain to a partner which mental strategy they used and why it worked for a given fact.

Sign in with your phone number to read the full note and download the GES plan - free.

Sign in with phone number

Curriculum details

Strand: Number (Strand 1)
Sub-strand: Number Operations (Addition, Subtraction, Multiplication and Division) (1.2)
Content standard: B2.1.2.3 - Develop and use strategies for mentally computing basic additions and subtraction facts to 19
Indicator: B2.1.2.3.1 - Use mental strategies for basic addition facts to 19 and related subtraction facts to 19
Suggested placement: Term 1, Week 10 (Week 10 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 1-3), 2019, p. 25
Transcribed from the official NaCCA publication. Check this page against the source.

Exemplars (from the NaCCA curriculum)

E.g. 1. Demonstrate fluency with addition and subtraction-related relationships by:
Quickly naming numbers that are 1, 2, or 10 more or less than a number between 1 and 100, or 5 more than a number that is a multiple of 5
Quickly Identifying the double of a number between 1 and 12
Add and subtract combinations to 10 quickly and accurately.
E.g. 2. Other sstrategies to use when adding
- 'counting up" when adding
- 'making doubles because doubles are easier to add (e.g., instead of 4 + 6 use 5 + 5)
- 'making doubles + or - 1 ' (e.g., instead of 4 + 5 use 4 + 4 + 1; instead of 4 + 5 use 5 + 5 -1)
'making 10s' (e.g., instead of 7 + 5 use 7 + 3 + 2; instead of 7 + 5 use 5 + 5 + )
E.g. 3. Some strategies to use when subtracting
- counting down (i.e., for 15 - 3, start at the big number, 15, and count on 3 places... 14, 13, 12. The answer is 12.) turning a subtraction into an addition, because additions are often easier (e.g., 7 - 3 = __ can be rephrased as 3 + __ = 7)