Download Chapter 2 Lesson 1: Rational Numbers

2-1
2-1 Rational
RationalNumbers
Numbers
Warm Up
Problem of the Day
Lesson Presentation
Course
Course
33
2-1 Rational Numbers
Warm Up
Divide.
1. 36  3
3. 68  17
12
4
5. 1024  64 16
Course 3
2. 144  6
4. 345  115
24
3
2-1 Rational Numbers
Problem of the Day
An ice cream parlor has 6 flavors of ice
cream. A dish with two scoops can have
any two flavors, including the same flavor
twice. How many different double-scoop
combinations are possible?
21
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2-1 Rational Numbers
Learn to write rational numbers in
equivalent forms.
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2-1 Rational Numbers
Vocabulary
rational number
relatively prime
Course 3
2-1 Rational Numbers
A rational number is any number that can
n
be written as a fraction
, where n
d
and d are integers and d  0.
Course 3
2-1 Rational Numbers
The goal of simplifying fractions is to make
the numerator and the denominator
relatively prime. Relatively prime
numbers have no common factors other
than 1.
Course 3
2-1 Rational Numbers
You can often simplify fractions by dividing
both the numerator and denominator by
the same nonzero integer. You can
12
simplify the fraction 15
to 45 by dividing
both the numerator and denominator by 3.
12 of the 15 boxes
are shaded.
12
15
4 of the 5 boxes
are shaded.
=
4
5
The same total area is shaded.
Course 3
2-1 Rational Numbers
Additional Example 1A: Simplifying Fractions
Simplify.
16
80
16 = 1 • 16 ;16 is a common factor.
80 = 5 • 16
16 ÷ 16
16
= 80 ÷ 16
80
1
=
5
Course 3
Divide the numerator
and denominator by 16.
Remember!
a = 1 for a ≠ 0
0 = 0 for a ≠ 0
a
a
–7= 7 = – 7
8
–8
8
2-1 Rational Numbers
Additional Example 1B: Simplifying Fractions
Simplify.
–18
29
18 = 2 • 9
29 = 1 • 29
–18
–18
=
29
29
Course 3
;There are no common
factors.
–18 and 29 are relatively prime.
2-1 Rational Numbers
Check It Out: Example 1A
Simplify.
18 = 3 • 3 • 2 ; 9 is a common factor.
27 = 3 • 3 • 3
18
27
18 = 18 ÷ 9
27 ÷ 9
27
=
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2
3
Divide the numerator
and denominator by 9.
2-1 Rational Numbers
Check It Out: Example 1B
Simplify.
17
–35
17 = 1 • 17 ; There are no common
factors.
35 = 5 • 7
17
17
=–
17 and –35 are relatively prime.
–35
35
Course 3
2-1 Rational Numbers
Decimals that terminate or repeat are rational
numbers.
To write a terminating decimal as a fraction,
identify the place value of the digit farthest to
the right. Then write all of the digits after the
decimal point as the numerator with the place
value as the denominator.
Course 3
2-1 Rational Numbers
Rational
Number
–3.2
0.16
Course 3
Description
Terminating
decimal
Repeating
decimal
Written as
a Fraction
–32
___
10
1
__
6
2-1 Rational Numbers
Additional Example 2: Writing Decimals as Fractions
Write each decimal as a fraction in simplest form.
A. 5.37
37
5.37 = 5
100
7 is in the hundredths place.
B. 0.622
0.622 =
622
1000
311
=
500
Course 3
2 is in the thousandths
place.
Simplify by dividing by the
common factor 2.
2-1 Rational Numbers
Check It Out: Example 2
Write each decimal as a fraction in simplest form.
A. 8.75
8.75 = 8
75
5 is in the hundredths place.
100
3
= 8
4
B. 0.2625
Simplify by dividing by the
common factor 25.
5 is in the
2625
0.2625 =
10,000 ten-thousandths place.
Simplify by dividing by
21
=
the common factor 125.
80
Course 3
2-1 Rational Numbers
To write a fraction as a decimal, divide the
numerator by the denominator. You can
use long division.
numerator
denominator
denominator numerator
Course 3
2-1 Rational Numbers
Additional Example 3A: Writing Fractions as
Decimals
Write the fraction as a decimal.
11
9
The fraction
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1 .2
9 11 .0
–9
20
–1 8
2
The pattern repeats.
Writing Math
A repeating decimal can be written
with a bar over the digits_that
repeat. So 1.2222… = 1.2.
11
is equivalent to the decimal 1.2.
9
2-1 Rational Numbers
Additional Example 3B: Writing Fractions as
Decimals
Write the fraction as a decimal.
7
20
0.3 5 This is a terminating decimal.
20 7.0 0
–0
70
–6 0
1 00
–1 0 0
0 The remainder is 0.
The fraction
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7
is equivalent to the decimal 0.35.
20
2-1 Rational Numbers
Check It Out: Example 3A
Write the fraction as a decimal.
15
9
The fraction
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1 .6
9 15 .0
–9
60
–5 4
6
The pattern repeats, so
draw a bar over the 6 to
indicate that this is a
repeating decimal.
15
is equivalent to the decimal 1.6.
9
2-1 Rational Numbers
Check It Out: Example 3B
Write the fraction as a decimal.
9
40
0.2 2 5 This is a terminating decimal.
40 9.0 0 0
–0
90
–8 0
1 00
– 80
200
– 2 00
0 The remainder is 0.
9
The fraction
is equivalent to the decimal 0.225.
40
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2-1 Rational Numbers
Lesson Quiz: Part 1
Simplify.
18
1.
42
3
7
15
2.
21
5
7
Write each decimal as a fraction in
simplest form.
5
27
–
3. 0.27
4.
–0.625
8
100
13
5. Write
as a decimal
6
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2.16
2-1 Rational Numbers
Lesson Quiz: Part 2
6. Tommy had 13 hits in 40 at bats for
his baseball team. What is his batting
average? (Batting average is the
number of hits divided by the number
of at bats, expressed as a decimal.)
0.325
Course 3