7th Grade Math

Rational Numbers

PART A B C

Multi-Part

Lesson 1

Get ConnectED

128 Rational Numbers

Terminating and Repeating

Decimals

NASCAR The table shows the

winning speeds for a 10-year

period at the Daytona 500.

1. What fraction of the speeds
   are between 130 and 145 miles
   per hour?


2. Express this fraction using
   words and then as a decimal.


3. What fraction of the speeds
   are between 145 and 165 miles
   per hour? Express this fraction
   using words and then as
   a decimal.

Our decimal system is based on powers of 10 such as 10, 100, and

1,000. If the denominator of a fraction is a power of 10, you can use

place value to write the fraction as a decimal.

Words Fraction Decimal

seven tenths _^7

10

0.7

If the denominator of a fraction is a factor of 10, 100, 1,000, or any

greater power of ten, you can use mental math and place value.

Use Mental Math

Write each fraction or mixed number as a decimal.

_^7

20

5 _^3

4

Think _^7

20

= _^35

100

× 5

× (^5 5) (^3)
4
= 5 + ^3
4
Think of it as a sum.
= 5 + 0.75 You know that ^34 = 0.75.
= 5.75 Add mentally.
So, ^7
20
= 0.35. So, 5 ^3
4
= 5.75.
a. ^3
10
b. 253 c. - 6 ^1
2
Main Idea
Write fractions as
terminating or
repeating decimals
and write decimals
as fractions.
Vocabulary
terminating decimal
repeating decimal
bar notation
Daytona 500
Year Winner Speed (mph)
1999 J. Gordon 148.295
2000 D. Jarrett 155.669
2001 M. Waltrip 161.783
2002 W. Burton 142.971
2003 M. Waltrip 133.870
2004 D. Earnhardt Jr. 156.345
2005 J. Gordon 135.173
2006 J. Johnson 142.667
2007 K. Harvick 149.335
2008 R. Newman 152.672
V
t
127_138_C3L1_895130.indd 128 12/31/09 12:34 PM