Download 8-1

8-1 Rational Numbers
Objective: Students will be able to write rational
numbers as decimals and decimals as fractions.
8.NS.1 Know that numbers that are not rational are called irrational. Understand informally
that every number has a decimal expansion; for rational numbers show that the decimal
expansion repeats eventually, and convert a decimal expansion which repeats eventually into
a rational number.
Do Now:
Rational Numbers on a Number Line
Integers
Whole Numbers
Natural Numbers
|
|
–4 –3
|
|
–2
|
|
–1
Negative numbers
|
|
|
0 1 2 3 4
Positive numbers
Zero is neither negative
nor positive
Another set of numbers you can display on a number line is
the set of rational numbers.
A rational number is any number that can be written in
the form a , where a and b are integers and b ≠ 0.
b
Some examples of rational numbers:
1

2
2
3
17
5
15
3
 14
 11
3
1
265
99
A rational number can also be expressed as a decimal
that terminates or as a decimal that repeats indefinitely:
1
2
2
3
17
5
15
3
 14
 11
3
1
=
=
=
=
=
=
 0.3
3.4
5
1.27
0.5
265
99
=
3 2.676767...
To express the rational number as a decimal, divide the
numerator (top) by the denominator (bottom)
numerator
denominator
denominator
numerator
Write
5
8
as a decimal:

2
Write 1 as a decimal:
3

In a recent season, St. Louis Cardinals first baseman Albert
Pujols had 175 hits in 530 at bats. What is his batting
average to the nearest thousandth?
Write 0.45 as a fraction:
Write 1.32 as a fraction:
Challenge!
Write
0.7 as a fraction:
Remember: Infinite repeating decimals are usually
represented by putting a line over (sometimes under) the
shortest block of
repeating decimals. Every infinite repeating
decimal can be expressed as a fraction.
1) Ask yourself, how many numbers repeat? 1 number
2) Assign a variable for the decimal. Let n = 0.77777
3) Assign power of 10 times the variable (how many numbers repeat).
Let 10n = 7.77777
4) Subtract variables and numbers.
5) Solve for n.
Write 0.5 as a fraction:

Write 2.1 8 as a fraction:

Glencoe Guided Practice
Page 10
Homework 8-1
Pages 11-12 All #’s
Exit Ticket:
Write convert the decimal into a fraction or the
fraction into a decimal in simplest form:
4
1)
5
5
2)5
16
3) 1.55
4)3.8