Number Operations (Addition… · B2 Mathematics

Lesson notes

Learning Objectives

Indicator: B2.1.2.1.1 - Use conceptual understanding of addition and subtraction to add, and subtract numbers to 100

By the end of the lesson, learners can:

Add a set of numbers in two different orders (e.g., 35 + 54 and 54 + 35) and explain why the sum stays the same.
Explain why adding 0 to a number or subtracting 0 from a number leaves the number unchanged (e.g., 27 + 0 = 27, 55 - 0 = 55).
Find the missing number in addition and subtraction sentences, including missing addend, missing subtrahend, and missing minuend (e.g., 34 + = 57, 27 - = 24, _ - 54 = 63).
Create their own addition or subtraction number sentence with a given answer and write a matching word problem (e.g., given the answer 53, create 30 + 23 = 53 and a word problem about oranges at the market).
Solve addition and subtraction problems within 100 using their understanding of how the operations work, not just memorised steps.

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Curriculum details

Strand: Number (Strand 1)
Sub-strand: Number Operations (Addition, Subtraction, Multiplication and Division) (1.2)
Content standard: B2.1.2.1 - Demonstrate conceptual understanding of operations of addition and subtraction with sums up to 100
Indicator: B2.1.2.1.1 - Use conceptual understanding of addition and subtraction to add, and subtract numbers to 100
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 1-3), 2019, p. 24
Transcribed from the official NaCCA publication. Check this page against the source.

Exemplars (from the NaCCA curriculum)

E.g. 1. Add a given set of numbers in two different ways (e.g. 35 + 54 and 54 + 35 or 18 + 12 + 3 and 3 + 18 + 12) and explaining why the order in which numbers are added does not change the sum
E.g. 2. Explain why the difference or sum is the same as the initial number when 0 is added or subtracted from a number (e.g., why 27 + 0 = 27 or 55 - 0 = 55)
E.g. 3. Match a word problem to a missing addend (e.g.,3 4 + ___ = 57), missing subtrahend1 (e.g. 27 - __ = 24) or missing minuend (__ - 54 = 63) statement
E.g. 4. Create an addition or subtraction number sentence and word problem for a number up to 100 (i.e., given the solution 53, create an addition or subtraction sentence with an answer of 53 and a corresponding word problem).
Footnote on the page: 1 A subtrahend is a number to be subtracted from another. In 7- 4 = 3, 4 is the subtrahend.