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W8 Whole Number Division and Multiplication

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This is classroom session taught by Yeap Ban Har on Day 1 of WSU Singapore Math Summer Institute. More than 70 participants took part in this institute - the second one in this university.

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W8 Whole Number Division and Multiplication

  1. 1. Session W8 Yeap BanHarWhole Numbers www.banhar.blogspot.com
  2. 2. Learning & Reviewing Basic FactsSome ways to help students acquire and consolidate basic facts.
  3. 3. 2x4=83x4=8+4
  4. 4. 2x4=84x4=8+8
  5. 5. 2x4=85 x 4 = 207 x 8 = 8 + 20
  6. 6. 10 x 4 = 40 9 x 4 = 40 – 4
  7. 7. Da Qiao Primary School, Singapore
  8. 8. She has 6. The product isWhat do I 48. have?
  9. 9. Multiplication & Division of Large NumbersSome ways to help students make sense of computation algorithm
  10. 10. Find the value of 34 x 2. 34 34 x2 x2 08 60 60 +8 68 68
  11. 11. Find the value of 34 x 3. 34 34 x3 x3 90 12 12 90
  12. 12. The concrete and the visualshelp develop meaning i.e.multiplying the tens and onesseparately.
  13. 13. 34 x3 90 12The expanded notationemphasizes 34 as 3 tens and4 ones which are then dealtwith separately.
  14. 14. Quantities with different‘nouns’ are dealt withseparately.
  15. 15. Find the value of 28 x 32 .To see 28 as 20 and8 and 32 as 30 and2.This leads to theidea of (a + b)(c +d).
  16. 16. x Use the digits 0 to 9 no more than once to make a correct multiplication sentence.The class had four solutions32 x 15 = 48012 x 65 = 78012 x 48 = 57639 x 12 = 46812 x 43 did not work.
  17. 17. 12 can be seen as 10 and 2.Thus, 12 x 65 can also be computed as the sum of 10 x 65 and 2x 65 i.e. 650 + 130.12 can be seen as 10 and 2.Thus, 39 x 12 can also be computed as the sum of 39 x 10 and39 x 2 i.e. 390 + 78.Alternatively, 40 x 12 can be used to compute 39 x 12.The use of number bonds to compute large numbers givesstudents opportunities to develop their number sense.
  18. 18. Find the value of 7081 3. Using number bonds, 7081 is 6000, 900, 180 and 1. Each is then divided by three.

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