Download 1.5: Rational Numbers

September 10, 2015
1.5: Rational Numbers
A rational number is a number that can be written as a quotient
of two integers, where the divisor is not 0.
Examples: 2/5, 0.3, -6, 3 1/2
Comparing Rational Numbers
-1/2 and -3/4
Method 1: Use a number line
Method 2: Re-write with common denominator
Your Turn ...
-2/3 and -1/6
September 10, 2015
Comparing Decimals
Example: Compare -4.4 and 4.7
Method 1: Use Number Sense
Method 2: Use a Number Line to illustrate
Ordering Rational Numbers
The peaks of four mountains or
seamounts are located either
below or above sea level as
follows: 1/4 mi, -0.2 mi, -2/9
mi, 1.1 mi. Put them in order
from least to greatest please.
The following temperatures were
recorded during a science project:
12 1/2ºC, -4ºC, 6.55ºC, and -6
1/4ºC. Order the integers from
least to greatest.
September 10, 2015
1-6: Adding and Subtracting Rational Numbers
The distance between two numbers on a number line is the absolute
value of their distance.
-5
-4
-3
-2
-1
0
1
2
3
4
5
Find the distance between -1.4 and 2.8
*Check by counting the distance on the number line.
Adding Rational Numbers
Same Sign
The sum of two positive rational
numbers is positive.
a. 1 3/4 + 2 1/8 =
Different Sign
Find the absolute value of each
addend. Subtract the lesser from
the greater. The sum has the sign
of the addend with the greater
absolute value.
c. 1 3/4 + (-2 1/8)
The sum of two negative rational
numbers is negative.
b. -3.5 + (-4.25) =
d. -3.5 + 4.25
September 10, 2015
Your Turn ....
1. -6.25 + (-8.55)
2. 4 3/5 + (-3 2/5)
Subtracting Rational Numbers
To subtract a rational number, add its opposite.
a. Find 6 2/3 - (-3 1/3)
b. Find -4.68 - (-5.79)
Your Turn ...
c. -3 2/5 - (- 2 4/5)
d. -13.45 - 12.25