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 ValueThe absolute value of a number n is the distance from n to 0 on a number line

Example 1Finding the Absolute Value

Simplify

a. │0│

b. │7.12│

c. │1 – ¾│

d. –│11 – 2│

Lesson Practice

Simplify

a. │– 3.4│

b. │6/7│

c. │14 + (–22)│

d. –│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 SignTo 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 SignsTo 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 2Adding Real Numbers

Find the sum.

a. (– 12) + (21)

b. (– 19) + (– 8)

c. (3.2) + (– 5.1)

d. (– 3/5) + (– 1/5)

Lesson Practice

Find the sum.

a. (–23.4) + 18.72

b. (– 2/3) + (– 1/6)

Example 3Identifying 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 4Application: 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.