Download Adding and Subtracting Notes

Investigation 2
Introducing
Addition and Subtraction
of Integers
New Vocabulary
•STEPS for
solving a problem
Problem #1
John has 8 video games and
his friend has 5. Together
they have 8 + 5 = 13 games.
How could you model this
problem using chips?
Problem #2
At a desert weather station, the temperature
at sunrise was 10 degrees Celsius. It rose
25 degrees Celsius by noon. The
temperature at noon was 10 +25 = 35
degrees Celsius.
How could you use a number line
to model this problem?
Adding Integers! READY? OK!
• If the signs are the same, you add the
numbers and keep the same sign!
• If the signs are the same, you add the
numbers and keep the same sign!
• If the signs are different, you find the
difference and keep the bigger sign!
• If the signs are different, you find the
difference and keep the bigger sign!
Integer Operations…to the tune of
Row, Row, Row your boat.
Same signs add and keep
Different signs subtract.
Take the sign of the larger number
Then you’ll be exact.
Multiply and Divide,
It’s an easy task.
Same signs positive
Different signs are not.
Adding Integers
Are the signs the
same?
Add the numbers and
keep the common sign.
Find the difference
Between the numbers
And keep the sign of
The larger number.
2.1 A
1. Find the sums in
each group.
2. Describe what the
examples in each
group have in
common.
3. Describe an
algorithm for
adding integers to
each group.
Group 1
2+8
-3 + -8
20 + 25
-24 + -12
Group 2
8 + -12
-3 + 2
14 + -23
-11 + -13
Now Let’s Practice.
1) -5 + 10 =________
2) 8 + -18 =________
3) 5 + (-9) =________
4) 2 + (-2) =________
5) -18 + 20 = _______
6) -11 + (-4)= _______
7) 20 + (-13) = ______
8) -25 + 20 = _______
9) 20 + (-30) = ______
10) -26 + (-4) = _____
11) -12 + 6 = ________
12) 65 + 5 = ________
13) 75 – 25 = ________
14) -50 + (-50) = _____
15) -22 + 5 = ________
16) -40 + 20 = _______
17) -36 + 44 = _______
18) -96 + 54 = _______
19) -84 + (-44) = _____
20) 72 + (-60) = ______
Complete B through D
in your textbook on
page 24 in the
Accentuate the
Negative section.
Challenge
Compute the following:
-5 + 7 + (-14) + (-9)
Investigation 2.2
Let’s review!
Example 1
Kim had 9 CD’s. She sold 4
CD’s at a yard sale. She
only has 9-4=5 of those CDs
left.
In this example, you are
taking away
objects from a set of objects.
Group 1
12 - 8
1.Find the differences in
each group.
-5 – (-7)
-4 – (-2)
2-4
2.What pattern do you
see in each group?
3. Describe an algorithm
for subtracting integers
in each group.
Group 2
12 – (-8)
-5 – 7
-4 – 2
2 – (-4)
Try these…
1. -1 – 3 = _____
2. -1 – ¾ = _____
3. -1 ½ - (-2) = _____
4. - 1 ½ - (-3/4) = _____
Are the expressions equal?
Think-Pair-Share…
1. -2 – 3 ___ 3 – (-2)
2. 12 – (-4) ___ -4 – 12
3. -15 – (-20) ___ -20 – (-15)
Let’s Practice
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
5 - 12
-2 - 6
6- (-16)
-11- (-7)
-13- (-12)
-14 – (-14)
11 – (-6)
9 – 17
-18 – (-12)
-20 - 7
•
•
•
•
•
•
•
•
•
•
32-40
28 – (-16)
-39 – (-13)
35 – 10
-32 – (-37)
50 – 99
64 – 101
-5 – 5
17-7
9 – (-11)
Summary
Without computing the answers, predict
how the answers in each pair will
compare. Will the answers be the same
or different? IF they are different, which
will be greater? Explain your answer.
1. -7 + (-8) and -7 – 8
2. -12 – (-4) and -4 – (-12)