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Announcements

Announcements. Last day to drop without a W is 12 February First exam: 13 February Class Notes in the Bookstore. Need by 19 February. Cost is $3.50. What is wrong with saying 372 base 6 ? What is a proper way of writing this number in base 6?. Let’s add in Alphabitia. BCD + DB

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Announcements

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  1. Announcements • Last day to drop without a W is 12 February • First exam: 13 February • Class Notes in the Bookstore. Need by 19 February. Cost is $3.50.

  2. What is wrong with saying 372 base 6? What is a proper way of writing this number in base 6?

  3. Let’s add in Alphabitia BCD+ DB BCD is DB is BCD + DB is

  4. You try: B0B+ABC Use the manipulatives or draw pictures to help explain your answer.

  5. Let’s subtract CBD - ADC = CBD is ADC is CBD - ADC is

  6. You Try… D00-B0B B0A-BD

  7. You try: Use manipulatives or drawings to explain BBC- A0C A0A0D- BCA

  8. Exploration 3.1 • In your groups: Do Part 1, #1 and #2a • Then do Part 2, #1 and 2

  9. 0 2 4 6 8 10 a b c Begin Addition • Ways to represent addition: • 1. Counters • 2. Number Line • 3. Part-Part Whole

  10. Vocabulary • A + B = C • A and B are called Addends • C is called the Sum • Since A + B = B + A every time, we give it a special name: commutative property. • Since A + (B + C) = (A + B) + C every time, we give it a special name: associative property.

  11. Addition and Place Value • If we have 154 + 69

  12. Mental Arithmetic • 39 + 57

  13. Mental Arithmetic • 39 + 57 • Leading digit (30 + 50) + (9 + 7) • Compensation (40 - 1) + 57 • Compensation (40 + 57) - 1 • Break and Bridge (39 + 50) + 7 • Compatible Numbers (39 + 51) + 6

  14. The name of the method is not important • Put down your pencil • 68 + 74 • How did you do this? • How might children do this?

  15. You try… • 23 + 96 • 489 + 723

  16. Estimation • Get a QUICK answer that is close but not exact!

  17. You will have 5 seconds • 382 - 147

  18. Estimation • 382 - 147 • Actual answer: 235 • Ways to estimate: • 380 - 150 = 230 • 400 - 150 - 20 = 230 • 375 - 150 = 225 • 385 - 145 = 240 • 390 - 140 = 250

  19. You try: • 45 + 87 • 391 + 1472

  20. Estimation vs. Exact Answer • Are the exact values of the addends given? • Is the exact value of the sum required? • In general: changing values (like population), measurement values (like distance), and predictions (like 35% chance of rain) are estimates

  21. Rounding • When you estimate, you are rounding to the nearest ten, hundred, million, etc. • If you round up, you are making an overestimation. • If you round down, you are making an underestimation.

  22. A problem: • I am thinking of 3 numbers whose sum is greater than 70. • Look at each statement below. Mark it as true or false. Be ready to explain why. • All three numbers are greater than 20. • If two of the number are less than 20, the other must be greater than 20.

  23. Explain the math • 348+ 472 10 11 7 • 820

  24. Explain the math • 471+ 299 10 160 600 • 770 • How is this different from the previous problem?

  25. Explain why the child made the mistake • 341 + 287 is the same as 340 + 290 + 7 + 3 • 749 + 684 is the same as 700 + 600 + 49 + 1 + 84 + 16 • 322 + 468 is the same as 320 + 460 • Would the mistake have been made if manipulatives had been used? Explain.

  26. Assignment • Section 3.1 p. 150-151#5, 6, 10, 24

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