Transcript 1 - Jefferson School District

4-1 Estimating with Fractions
California
Standards
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.
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, 1 , or 1.
2
You can use a number line to help.
0
3
10
1
2
1
3
is closer to than to 0.
2
10
Holt CA Course 1
1
4-1 Estimating with Fractions
You can also round fractions by comparing its
numerators with its denominators.
Holt CA Course 1
4-1 Estimating with Fractions
Example 1: Measurement Application
3
A blue whale can grow to 33 5 m long, while
1
the great white shark may be as long as 4 2 m.
Estimate how much longer the blue whale is
than the great white shark.
33 3 – 4 1
2
5
1
1
1
Round each mixed
33 3
4
4
33
2
2
5
2
number.
1 – 1 = 29
Subtract.
33
4
2
2
The blue whale is about 29 m longer than the
great white shark.
Holt CA Course 1
4-1 Estimating with Fractions
Example 2: Estimating Sums and Differences
Estimate each sum or difference.
A. 7 – 2
9
B.
5
2
7
1
5
9
1– 1=1
2 2
45+ 31
8
9
45
41
9
2
1
41+ 3 = 7
2
2
Holt CA Course 1
1
2
Round each fraction.
Subtract.
31
8
3 Round each mixed fraction.
Add.
4-1 Estimating with Fractions
Example 2: Estimating Sums and Differences
Estimate the difference.
C.
1
21 –
12
8
21
8
2
1
12
2–0=2
Holt CA Course 1
0
Round each number.
Subtract.
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
1
to 2 , round the mixed number
up to the next whole number. If the
fraction is less than 12 , round down to a
whole number by dropping the fraction.
Holt CA Course 1
4-1 Estimating with Fractions
Example 3A: Estimating Products and Quotients
Estimate each product or quotient.
32 • 65
6
9
32
3
9
65
6
7
3 • 7 = 21
Holt CA Course 1
Round each mixed number to
the nearest whole number.
Multiply.
4-1 Estimating with Fractions
Example 3B: Estimating Products and Quotients
Estimate each product or quotient.
13 4 ÷ 2 1
4
5
13 4
14
5
21
4
2
14 ÷ 2 = 7
Holt CA Course 1
Round each mixed number to
the nearest whole number.
Divide.
4-1 Estimating with Fractions
Check It Out! Example 1
A Cocker Spaniel may grow to weigh about
1
11 2 kilograms while the Chihuahua may
7
weigh about 2 8 kilograms. Estimate how
much more the Cocker Spaniel weighs than
the Chihuahua.
11 1 – 2 7
8
2
7
Round each mixed
11 1
3
2
11 1
8
2
2
number.
1
11 – 3 = 8 1
Subtract.
2
2
The Cocker Spaniel weighs about 8 1 kg more.
2
Holt CA Course 1
4-1 Estimating with Fractions
Check It Out! Example 2
Estimate the difference.
8
42 –
15
9
42
9
4
1
1
=
–
3
4
2
2
Holt CA Course 1
8
15
1
2
Round each number.
Subtract.
4-1 Estimating with Fractions
Check It Out! Example 3
Estimate each product or quotient.
11 7 ÷ 3 1
3
8
11 7
12
8
31
3
3
12 ÷ 3 = 4
Holt CA Course 1
Round each mixed number to
the nearest whole number.
Divide.