Warm up problem: What is wrong with saying 372 base 6? What is a better way of writing this number in base 6? - PowerPoint PPT Presentation

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Warm up problem: What is wrong with saying 372 base 6? What is a better way of writing this number in base 6?

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Warm up problem: What is wrong with saying 372 base 6? ... 89 Minuend - 24 Subtrahend. 65 Difference. Strategies. Break the number apart ... – PowerPoint PPT presentation

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Title: Warm up problem: What is wrong with saying 372 base 6? What is a better way of writing this number in base 6?


1
  • Warm up problem What is wrong with saying 372
    base 6? What is a better way of writing this
    number in base 6?

2
Exploring Addition
  • Addition in Alphabitia
  • Exploration 3.1, Part 1
  • Use manipulatives to help you

3
Homework for Wednesday
  • Read Section 3.1 in the textbook
  • Exercises pp. 150-151 5, 6, 24

4
Important announcements
  • First exam Wednesday, September 19th1.2, 1.3,
    1.4, 1.7 2.3 3.1, 3.2 and Explorations
  • Last day to drop without a W is 9/14
  • Pick up 302A packet at the bookstore--need by
    Monday, September 17th

5
Mental addition
  • 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

6
Ways to represent addition
  • 1. Counters
  • 2. Number Line
  • 3. Part-Part Whole

7
Vocabulary of addition
  • 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.

8
Addition and Place Value
  • If we have 154 69

9
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

10
No pencils!
  • 23 96
  • 489 723

11
Estimation
  • Get a QUICK answer that is close but not exact!

12
5 seconds to get a quick estimate
  • 382 - 147

13
Estimation methods
  • 382 - 147
  • Actual answer 235
  • Ways to estimate
  • 380 - 150 230
  • 400 - 150 - 20 230
  • 375 - 150 225
  • 385 - 145 240
  • 390 - 140 250

14
You try some
  • 45 87
  • 391 1472

15
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

16
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.

17
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.

18
Explain the math
  • 348 472 10 11 7__
  • 820

19
Explain the math
  • 471 299 10 160 600
  • 770
  • How is this different from the previous problem?

20
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.

21
Subtraction
  • Take-away
  • Comparison

22
Subtraction vocabulary
  • 89 Minuend
  • - 24 Subtrahend
  • 65 Difference

23
Strategies
  • Break the number apart
  • Using negative numbers
  • Adding up

24
The Standard Algorithm
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