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Unit 2
Estimation and Computation
Use the following number 5, 678.231 to answer questions 1 and 2.
1. What digit is in the hundreds place?
a. 5
b. 6
c. 3
d. 1
2. What digit is in the tenths place?
a. 2
b. 3
c. 1
d. 7
3. Without using computation, what is 34 * 10,000?
a. 34, 000
b. 3, 400
c. 340, 000
d. 3, 400, 000
Lesson 2-1: Place Value
3,057,129.486
What value is the digit 5
ten thousand
What value is the digit 6
What value is the digit 2
tens
What value is the digit 0
hundred thousand
thousandths
What value is the digit 8
hundredths
What value is the digit 3
millions
What value is the digit 1
hundred
What value is the digit 4
tenths
Lesson 2-1: Rules of Rounding
• underline place value you are rounding to
• look one place to the right
• 5 or more raise the score
• 4 or less let it rest
• all numbers to the left of underlined number stays the same
Examples:
4,827 rounded to the nearest ten is 4,830
4,827 rounded to the nearest hundred is 4,800
4,827 rounded to the nearest thousand is 5,000
Round each number to the nearest...
number
1
10
100
1,000
3,471.2
3,471
3,470
3,500
3,000
12,673
12,673
12,670
12,700
13, 000
75,485.6
75,486
75,490
75,500
75,000
3,286
3,286
3,290
3,300
3,000
4,249.7
4,250
4,250
4,200
4,000
6,810.8
6,811
6,810
6,800
7,000
Round each number to the nearest...
Number
100
10
1
0.1
0.01
550
549.8
549.81
549.812
500
550
2.8907
X
X
3
2.9
2.89
4,408.93
4,400
4,410
4,409
4,408.9
4,408.9
8.5439
X
X
9
8.5
8.54
Fill in the blanks using <, >, or =
>
34.5 _____ 34
>
0.245 _____ 0.25
>
0.1 _____0.100
>
1.245 _____0.345
>
0.201 _____0.21
>
0.24 _____0.24000
>
0.045 _____0.450
>
0.65 _____0.0065
>
1,234.05 _____1,234.06
Classwork:
1. Begin rounding and place value packet
If time:
2. Math Box 2- 1 (p. 31)
3. Extra Credit
Lesson 2-2: Expanded Notation
Standard Notation
123
39.02
4,916
5.78
302.6
90.005
Expanded Notation
100 + 20 + 3
30 + 9 + 0.02
4,000 + 900 + 10 + 6
5 + 0.7 +
0.08
300 + 2 + 0.6
90 + 0.005
Lesson 2-2: Partial Sums
Addition
348
+ 177
2064
+ 382
359
+ 298
Keep an open
mind. When
working on your
own, you only
need to use this
strategy for one
problem.
2419
+ 536
Remember to line up the decimal
points
22.62
4.65
+ 1.7
+ 3.25
5.8
+ 2.49
Classwork:
1. Complete journal page 3233
If time:
2. Math Box 2-2 (p. 34)
3. Extra Credit
Lesson 2-3: Trade First
463
- 275
809
- 537
Keep an open
mind. When
working on your
own, you only
need to use this
strategy for one
problem.
600
- 397
67.35
- 9.59
89.67
- 2.98
50.30
- 2.42
Classwork:
1. Complete journal page
35
If time:
2. Math Box 2-3 (p. 36)
3. Extra Credit
Lesson 2-4: Addition and Subtraction Number Stories
Number
Sentences
• Use math symbols instead of
Open Number
• contain a variable -letter that
Sentences
words
represents a
number
• can be true or false
• must use a relation symbol =,
<,
>
• must use an operational symbol +, - *,
÷
Examples
2+2=4
true
6 * 4 > 2 + 8 true
3<9
false
Examples
Solution
(variable equals)
5 + B = 12
B=7
D÷3=8
D = 24
3*4=V
V = 12
120 - C =
60
C = 60
Answer
(unit label)
At breakfast, the temperature
outside was 47˚F. By lunchtime,
the temperature was 63˚F. How
many degrees warmer was it by
lunchtime?
Open number sentence
Solution:
Open number sentence
Answer:
Mary had $32.50 in her savings account.
After she withdrew some money, she
had $17.25 left. How much money did
she withdraw?
Open number sentence
Solution:
The school library has 486
fiction books and 321 non
fiction books. How many
books does the library have in
all?
Solution:
Answer:
Mr. Snow is 49 years old. Her son,
Kevin, is celebrating his 24th birthday
today. Mr. Snow is 6 years older than
Mrs. Snow. How old was Mrs. Snow
when Kevin was born?
Open number sentence
Answer:
Solution:
Answer:
Classwork:
1. Complete journal page 37 &
38
If time:
2. Math Box 2-4 (p. 39)
3. Extra Credit
Lesson 2-5: Statistical Landmarks
Minimum: lowest number
Maximum: highest number
Range: highest number minus the lowest
Mode: the number that occurs most often.
there can be one mode, more than one
or none
Median: the middle number when all the
numbers
are arranged in numerical order.
Mean: the average - add all the numbers, divided
by
the number of numbers you have.
Practice:
10, 7, 1, 2, 10, 6, 4,
8
minimum
maximum
range
mode
median
mean
Classwork:
1. Complete journal page 40 41
If time:
2. Math Box 2-5 (p. 42)
3. Extra Credit
Lesson 2-7: Magnitude Estimates
Lesson 2-8: Multiplication of Whole Numbers & Decimals
Lesson 2-10: Powers of ten