B3 Mathematics · Term 1, Week 11
Number Operations (Addition, Subtraction, Multiplication and Division)
Lesson notes
Learning Objectives
Indicator: B3.1.2.4.2 - Use a variety of personal and standard strategies to solve different types of subtraction and addition equations and problems with missing numbers in all positions
By the end of the lesson, learners can:
- Use at least two different personal or standard strategies (e.g., partial sums, friendly jumps, compensation, constant difference) to solve addition problems within 1000.
- Use at least two different strategies (e.g., decomposing the subtrahend, counting up, compensation, constant difference) to solve subtraction problems within 1000.
- Find a missing addend in equations such as 348 + ? = 615 and ? + 279 = 502 using a chosen strategy.
- Find a missing number in subtraction equations with the missing number in any position, such as 800 - ? = 356, ? - 254 = 198, and 673 - 198 = ?.
- Explain and justify the strategy they chose for a given problem, showing why their answer is correct, and check their work using a different strategy.
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Sign in with phone numberCurriculum details
- Strand
- Number (Strand 1)
- Sub-strand
- Number Operations (Addition, Subtraction, Multiplication and Division) (1.2)
- Content standard
- B3.1.2.4 - Develop and apply personal and standard strategies for adding and subtracting within 1000
- Indicator
- B3.1.2.4.2 - Use a variety of personal and standard strategies to solve different types of subtraction and addition equations and problems with missing numbers in all positions
- Suggested placement
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Term 1, Week 11
(Week 11 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.
- Source document note
-
The official curriculum document has a fault in this entry, so the curriculum text above is transcribed exactly as printed:
- exemplars - p.50
- Curriculum reference
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Mathematics Curriculum for Primary Schools (Basic 1-3), 2019, p. 50
Transcribed from the official NaCCA publication. Check this page against the source.
Exemplars (from the NaCCA curriculum)
E.g. 1. Splitting or partial sums, or adding 100s together first, then 10s together, then 1s, and then adding those partial sums together (see example of 168 + 384 to right) Eg. 2. Adding on by friendly jumps strategy, where one of the numbers is decomposed into a friendlier number and added in "chunks" (for example, when adding 326 + 232, start with326, add 100 two times to get 526 (326 + 100 + 100), then add on 10 three times to get 556 (526 + 10 + 10 + 10) and then add on 2 to get 558. The answer is 558. E.g. 3. Making 10s or 100s when adding a number that is close to a multiple of 10 or 100 by moving a quantity from one number to another, for example when adding 296 + 568, move 4 from 568 to 296 to make 300 (see example to right)
E.g. 4. Compensation strategy - adding more than is required to create an easier number to add - usually a multiple of 10 or 100 - and then subtracting that same amount from the answer (for example, when adding 126 + 39, add 1 to 39 to create the expression 126 + 40, which gives 166, then subtract from the answer the 1 that was added; 166 -1 = 165, so the answer is 165) E.g. 5. Decomposing or splitting the second number into partial subtractions that are easier to subtract (e.g. when subtracting 127 - 38, decompose 38 and subtract in friendlier jumps - 127 - 20- 10- 8 or see examples in text boxes) E.g. 6. Starting at the second number and counting up in friendly jumps (e.g., when subtracting 127 - 18, start at 18 and count up by 100 to get 118, then count up 9 to get 127...so the answer is 109)
E.g. 7. Compensation strategy - Subtracting more than is required (to turn the 2 nd number into a friendlier number), then adding the extra amount to the answer (for example, when subtracting 547 -296, subtract 547 - 300 = 247, then add 4 to the answer to get 251) E.g. 8. Constant difference - Adding (or subtracting the same amount from each number to make one number "friendlier", knowing that it does not change the answer (e.g., instead of 158 - 47, do 161 - 50 which is 111). E.g. 1 says "see example of 168 + 384 to right" but the printed page shows no such worked example beside it.