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Holt CA Course 1
4-1 Estimating with Fractions
Warm UpWarm Up
California StandardsCalifornia Standards
Lesson PresentationLesson Presentation
PreviewPreview
Holt CA Course 1
4-1 Estimating with Fractions
1. 5.2x = 127.92
2. = 64.2
3. 2.6 =
Warm UpSolve.
x = 24.6
x = 39.26
x = 263.22 x t 4.1
x 15.1
Holt CA Course 1
4-1 Estimating with Fractions
Prep for NS2.1 Solve problems involving addition, subtraction, multiplication, and division of positive fractions and explain why a particular operation was used for a given situation.
California Standards
Holt CA Course 1
4-1 Estimating with Fractions
Sometimes, when solving problems, you may not need an exact answer. To estimate sums and differences of fractions and mixed numbers, round each fraction to 0, , or 1. You can use a number line to help.
12
12
0 1310
is closer to than to 0.12
310
Holt CA Course 1
4-1 Estimating with Fractions
You can also round fractions by comparing itsnumerators with its denominators.
Holt CA Course 1
4-1 Estimating with Fractions
Additional Example 1: Measurement ApplicationA blue whale can grow to 33 m long, while
35
the great white shark may be as long as 4 m.
12
Estimate how much longer the blue whale is than the great white shark.
3335
– 4 12
3335
3312
4 12
4 12
Round each mixed number.
Subtract.
The blue whale is about 29 m longer.
= 29–3312
4 12
Holt CA Course 1
4-1 Estimating with FractionsCheck It Out! Example 1
1112
– 2 78
1112
1112
2 78
3 Round each mixed number.
Subtract.= 8–1112
3 12
A Cocker Spaniel may grow to weigh about11 kilograms while the Chihuahua may weigh about 2 kilograms. Estimate how much more the Cocker Spaniel weighs than the Chihuahua.
78
12
The Cocker Spaniel weighs about 8 kg more.12
Holt CA Course 1
4-1 Estimating with Fractions
Estimate each sum or difference.
Additional Example 2: Estimating Sums and Differences
A. 79
– 25
1 25
1 2
1 – =
79
Round each fraction.
Add.
59
B. 4 + 3 18
4 59
4 12
318
3Round each mixed fraction.
Subtract.
4 12
+ 3 = 7 12
1 2
1 2
Holt CA Course 1
4-1 Estimating with Fractions
Estimate the difference.
Additional Example 2: Estimating Sums and Differences
Subtract.
18
C. 2 – 1 12
218
2 Round each number.
1 12 0
2 – 0 = 2
Holt CA Course 1
4-1 Estimating with Fractions
Estimate each sum or difference.
Check It Out! Example 2
A. 78
– 16
1 16
0
1 – 0 = 1
78
Round each fraction.
Add.
35
B. 5 + 2 29
5 35
5 12
229
2Round each mixed fraction.
Subtract.
5 12
+ 2 = 7 12
Holt CA Course 1
4-1 Estimating with Fractions
Estimate the difference.
Check It Out! Example 2
Subtract.
29
C. 4 – 8 15
4 29
4 Round each number.
8 15
12
12
– = 3 12 4
Holt CA Course 1
4-1 Estimating with Fractions
You can estimate products and quotients of mixed numbers by rounding to the nearest whole number. If the fraction in a mixed number is greater than or equal to , round the mixed number up to the next whole number. If the fraction is less than , round down to a whole number by dropping the fraction.
12
12
Holt CA Course 1
4-1 Estimating with Fractions
Additional Example 3A: Estimating Products and Quotients
Estimate each product or quotient.
3 • 7 = 21 Multiply.
29
3 • 656
329
3
656
7
Round each mixed number to the nearest whole number.
Holt CA Course 1
4-1 Estimating with Fractions
Additional Example 3B: Estimating Products and Quotients
Estimate each product or quotient.
14 ÷ 2 = 7 Divide.
45
13 ÷ 2 14
13 45
14
214
2
Round each mixed number to the nearest whole number.
Holt CA Course 1
4-1 Estimating with Fractions
Check It Out! Example 3A
Estimate each product or quotient.
8 • 3 = 24 Multiply.
23
7 • 234
723
8
234
3
Round each mixed number to the nearest whole number.
Holt CA Course 1
4-1 Estimating with Fractions
Check It Out! Example 3B
Estimate each product or quotient.
12 ÷ 3 = 4 Divide.
78
11 ÷ 3 13
11 78
12
313
3
Round each mixed number to the nearest whole number.
Holt CA Course 1
4-1 Estimating with FractionsLesson Quiz
Estimate each sum or difference.
1. The new show arena being built in Franklin County is 150 feet long and 110 feet wide. Estimate
the difference between the length and width.
34
12
2. 59
+ 45
3. 78
– 37
4. 9 34
– 615
5. 5 • 2
4
40 ft
112
12
12
Estimate each product or quotient. 78
16
6. 17 ÷ 3 656
13