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 = 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 = 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 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

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 Group

Now Let’s Practice. 1) =________ 2) =________ 3) 5 + (-9) =________ 4) 2 + (-2) =________ 5) = _______ 6) (-4)= _______ 7) 20 + (-13) = ______ 8) = _______ 9) 20 + (-30) = ______ 10) (-4) = _____ 11) = ________ 12) = ________ 13) 75 – 25 = ________ 14) (-50) = _____ 15) = ________ 16) = _______ 17) = _______ 18) = _______ 19) (-44) = _____ 20) 72 + (-60) = ______

Complete B through D in your textbook on page 24 in the Accentuate the Negative section.

Challenge Compute the following: (-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 – (-7) -4 – (-2) Group 2 12 – (-8) -5 – 7 -4 – 2 2 – (-4) 1.Find the differences in each group. 2.What pattern do you see in each group? 3. Describe an algorithm for subtracting integers in each group.

Try these… 1.-1 – 3 = _____ 2.-1 – ¾ = _____ 3.-1 ½ - (-2) = _____ ½ - (-3/4) = _____

Are the expressions equal? Think-Pair-Share… 1.-2 – 3 ___ 3 – (-2) 2.12 – (-4) ___ -4 – – (-20) ___ -20 – (-15)

Let’s Practice (-16) (-7) (-12) – (-14) 7.11 – (-6) 8.9 – – (-12)

– (-16) -39 – (-13) 35 – – (-37) 50 – – – – (-11)

Summary (-8) and -7 – – (-4) and -4 – (-12) 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.