Whole Numbers Addition & Subtraction

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Whole Numbers Addition & Subtraction

  1. 1. Whole NumbersAddition & Subtraction Marshall Cavendish Institute Peggy Foo
  2. 2. Learning Outcomes State the purpose of number bonds Use addition and subtraction strategies
  3. 3. Number Bonds Number bonds are different combinations of numbers that make up a given number.
  4. 4. Different Types of Bonds 67 - 56 = 11 7 – 1 + 5 x 2 = 16 2+3=5 80 ÷ 10 = 8 7 X 8 = 56
  5. 5. Purposes Number bonds lay a strong foundation for learning addition and subtraction efficiently. Number bonds also enhance mental computations
  6. 6. Activities for Lower Grades Using the magnets and 10-frame How many bonds are there to make 10?
  7. 7.  Use concrete manipulative Generate different possible ways/ bonds Move to pictorial stage
  8. 8. Extension What are the different sums that you can get with different sets of whole numbers? What can you observe? What can you observe about the number in the middle? What can you observe about the sums?
  9. 9.  Open-ended task (with more than 1 sum) Generate different possible ways/ bonds Problem-solving task
  10. 10. Addition Strategies using Number Bonds  Near-10 Strategy12 13 3
  11. 11.  The Doubles Strategy12 13 3
  12. 12. Addition Strategies using NumberBonds Near-100 Strategy 245 + 98
  13. 13. Addition Strategies using NumberBonds Near-100 Strategy 245 + 98Rewrite 98 as (100-2)Add 245 + 100 = 345We add more than we should345 – 2 = 343
  14. 14. Debriefing The ability to see numbers in different combinations is developing number sense/ number concept.
  15. 15. How many ways to find the value of 43 + 29
  16. 16. Additional Strategies using NumberBonds Using Hundred Chart 43 + 29 = 43 + 30-1 (near-ten strategy) = 73-1 = 72 43 + 29 = 60 + 12 (place value concept) = 72
  17. 17. Subtraction Strategies usingNumber Bonds Addition bonds for Subtraction16 – 9
  18. 18. Subtraction Strategies usingNumber Bonds Addition bonds for Subtraction16 – 916 is made up of (10 + 6)Use 10 – 9 = 1Add 1 to 6 (remaining number in the bond)1+6=7
  19. 19. Subtraction Strategies usingNumber Bonds Near-100 Subtraction Strategy256 - 97
  20. 20. Subtraction Strategies usingNumber Bonds Near-100 Subtraction Strategy256 - 97Rewrite 97 as (100 – 3)256 – 100 = 156Subtract more than we should156 + 3 = 159
  21. 21. How many ways to find thevalue of 67- 49
  22. 22. Subtraction (renaming once) 67-49 = 67-50 +1 (near 10 strategy) = 17+1 = 18 67-49 = 18 (place value concept)
  23. 23. Place Value Concept To add and subtract using formal algorithms Use place value concept to develop conceptual understanding Use base ten
  24. 24. Summary Concrete-Pictorial-Abstract Approach Aim to develop conceptual understanding before procedural understanding (Richard Skemp)
  25. 25. Summary Mental Strategies Formal Algorithm involving number bondsAddition Strategies: Place value concept1) Near-10 Strategy2) The doubles Strategy3) Near-100 StrategySubtraction Strategies:1) Addition Bonds forsubtraction2) Near-100 SubtractionStrategy

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