Download Lesson 5

Bell Quiz
Objectives
• Find absolute value and add signed
numbers.
Finding Absolute Value
• The absolute value of a number is the
distance from the number to zero on a
number line.
• The absolute value of 4 is written │4│.
│4│= 4
│– 4│= 4
Absolute Value
The absolute value of a number n is the distance from n to 0 on a number line
Example 1
Finding the Absolute Value
Simplify
a.
b.
c.
d.
│0│
│7.12│
│1 – ¾│
–│11 – 2│
Lesson Practice
Simplify
a.
b.
c.
d.
│– 3.4│
│6/7│
│14 + (–22)│
–│7 + 16│
Modeling Real Number Addition
Find the sum of:
–5 + 3
(-)(-)(-)(-)(-)
(+)(+)(+)
Modeling Real Number Addition
a. 4 + (– 3)
b. – 2 + – 6
c. (– 7) + (7)
d. The sum of two positive numbers is always
positive.
e. The sum of two negative numbers is always
negative.
f. The sum of a positive and a negative number is
always negative.
Rules for Adding Real Numbers
Adding Numbers With the Same Sign
To add numbers with the same sign, add their absolute values. The
sum will have the same sign as the addends.
Examples
3+2=5
– 3 + (– 2) = – 5
Adding Numbers With Different Signs
To add numbers with different signs, find the difference of their
absolute values. The sum will have the sign of the addend with the
greater absolute value.
Examples
3 + (– 2) = 1
(– 3) + 2 = – 1
Example 2
Adding Real Numbers
Find the sum.
a.
b.
c.
d.
(– 12) + (21)
(– 19) + (– 8)
(3.2) + (– 5.1)
(– 3/5) + (– 1/5)
Lesson Practice
Find the sum.
a. (–23.4) + 18.72
b. (– 2/3) + (– 1/6)
Example 3
Identifying Sets of Real Numbers Closed Under Addition
Determine whether each statement is true or
false.
a. The set of integers is closed under
addition.
b. The set of real numbers is closed under
addition.
Lesson Practice
Determine whether each statement is true or
false.
a. The set of rational numbers is closed
under addition.
b. The set of positive integers is closed
under addition.
Example 4
Application: Football
On first down, the Silver Wolves lost 4
yards. They gained 7 yards on second
down. Use addition to find the total
number of yards they will need to pick up
in order to gain a first down.
Lesson Practice
The temperature at 7:00 p.m. was 34°F.
The temperature fell 12°F by midnight.
Use addition to find the temperature at
midnight.