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Calculate Strategies and Algebra

Calculate Strategies and Algebra. Students must have a deep understanding of numbers, how they work and the relationship between them, to be successful at algebra The Mathematics Australian Curriculum is at least 70% algebra in Year 9

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Calculate Strategies and Algebra

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  1. Calculate Strategies and Algebra • Students must have a deep understanding of numbers, how they work and the relationship between them, to be successful at algebra • The Mathematics Australian Curriculum is at least 70% algebra in Year 9 • Using an algorithm provides none of the essential understandings needed for algebra

  2. Many Calculate Strategies Require a Thorough Understanding of Place Value Asked to expand 463 most students will write: 400 + 60 + 3 and it appears they understand place value. If a child is struggling with the calculate strategies at school, they almost always do not understand place value. 2 6 When asked to show where the ‘2’ is, student’s who don’t understand place value will point to 2 ones

  3. Partitioning Multiply by the tens and then the ones. e.g. 6 x 27 is 6 x 20 add 6 x 7, so 120 add 42, which is 162

  4. Distributive LawPartitioning to Multiply 16 x 4 = 10 x 4 = 40 + 6 x 4 = 24 It is a small step to understanding that 16a is the same as 10a+6a

  5. Multiplying Larger Numbers, The Distributive Law - Partitioning 13 x 16 (10x10 + 10x6) + (3x10 + 3x6) Primary students are not expected to apply this law to algebra. This slide shows the links between the calculate strategy and how it will assist the development of algebra (a + b) x (a + c) = (a² + ac) + (ba + bc)

  6. Commutative LawTurn Arounds a + b = b + a (a+b)+c = a+(b+c) This begins in Kindy when we drop a collection of 5 objects and ask children what they can see. “I can see a 3 and 2 and that’s 5” “I can see a 2 and 3 and that makes 5” a - b ≠ b - a

  7. Compensate to Add 8 + 4 = 10 + 2 = This strategy might also be called Bridge to Ten

  8. 9 + 7 = 10 + 6 =

  9. 24 + 18 = 22 + 20 =

  10. Solving Algebraic Equations The Part-Part-Whole Model • The Part-Part Whole Model is used to develop an understanding about the relationship between addition and subtraction • Students are exposed to the language of part-part-whole from Kindy and begin to see the model being used in pre-primary. They should understand the model by the end of Year 3.

  11. Developing the Part-Part-Whole Model 7 + ? = 10 If we know the whole amount and one of the parts, we choose subtraction to solve the problem 10 – 7 = ? If we know both parts we choose addition to solve the problem 7 + 3 = ? 10 - ? = 7 can be solved by 10 – 7= ? And ? = 10 -7 ? = 3 10 – n = 7 n = 10 – 7 n = 3

  12. Using the Part-Part-Whole Model Susan had some books on her bookshelf. She bought 7 more books and put them on her bookshelf too. Now there are 25 books on her bookshelf. How many books did Susan have before she went shopping? Write the equation that matches the story. ? + 7 = 25 Children solve problems like this in Years 2 and 3. They solve similar problems using smaller numbers in Pre-Primary and Year 1 Write the calculator equation 25 – 7 =

  13. Compensate to Subtract 4 -2 = 5 - 3

  14. Compensate to Subtract Children need to understand that if you add or subtract the same amount to each number, the answer will be the same. This understanding takes a long time to develop. 83 – 68 = 85 – 70 = 172 – 94 = 178 - 100

  15. Front Loading 24 + 33 = 20 + 30 = 50 4 + 3 = 7 50 + 7 = 57

  16. Front Loading 24 + 33 = 24 + 30 = 54 54 + 3 = 57

  17. Our aim is to teach Mathematics in a way that develops deep understandings. These understandings allow students to work with abstract ideas and be successful in Maths in the long term. • Teaching mathematical understandings is necessarily slow. • Sharon.Oldfield@education.wa.edu.au

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