ADDING INTEGERS WITH THE SAME SIGN
Do Now:
How do you add integers with the same sign?
A football team has a loss of 3 yards on their first play and a loss of 11 yards on their second
play. Express their total yards loss as an integer.
WARM UP
Write the integer for each situation.
1.
An elevator ride down 27 stories
2.
A $700.00 profit
3.
46 degrees below zero
4.
A gain of 12 yards
Find the sum or difference.
5.
183 + 78 =
7. 677 – 288 =
6.
1188 + 902 =
8. 2647 – 1885 =
WARM UP
1. -8 + (-1) =
=
5. -3 + (-7)
2. -48 + (-12) =
6. -32 + (-38) =
3. 109 + 191 =
7. -40 + (-105) =
4. -150 + (-1500) = 8. -200 + (-800)
=
ADDING INTEGERS WITH A COMMON SIGN
When adding integers with the same sign, add the absolute values of the integers and
use the sign of the integers for the sum.
Absolute value refers to the integer’s distance from zero on a number line.
Positive integers are always to the right of zero and negative integers are always to
the left of zero.
What do the following expressions have in common?
-7 + (-6) =
7+6=
What is different about them?
Hint: Use a number line to help you explain.
OPPOSITES
Integers that have the same absolute value, but different signs, are known as
opposites. They have the same distance from zero, but they are in opposite
directions.
Example: 5 and (-5)
Both integers are five units from zero on the number line.
-15
-10
-5
0
5
10
15
Can we use the same method to add two positive integers?
COMMUTATIVE PROPERTY
The commutative property for addition allows us to add integers in any order, if and
only if the operational sign stays the same throughout the expression.
7+6=6+7
13 = 13
3+5+4=5+4+3
12 = 12
Does this property work for adding two negative integers?
Suppose the temperature is -1◦F and
drops by 3◦F? Explain how to use the
number line to find the new
temperature.
How would using a number line to find the
sum 2 + 5 be different from using a
number line to find the sum -2 + (-5)?
Can you find two different negative
integers that have the same sum as
-2 + (-5)?
CHALLENGE TIME
1.
Choose any two negative integers.
2.
Is the sum of the integers less than or greater than the value of either of the
integers?
3.
Will this be true no matter which two integers we choose? Explain.
EXIT TICKET
1.
-76 + (-124) =
2.
-12 + (-66) + (-48) =
3.
A football team receives a 5 yard penalty on one play and a ten yard penalty on the next.
Write a sum of negative integers to represent this situation.
4.
Eli had mini golf scores of -3, -4, and -3. What was his total score for the three rounds?
5.
Anna made withdrawals from her bank account of $60, $85, and $115. Write and
solve an addition problem that shows her withdrawals as negative integers.