9. Negative Numbers Are Used to Measure Under Sea Level 0 10 20 30 -10 -20 -30 -40 -50
10. Negative Numbers Are Used to Show Debt Let’s say your parents bought a car but had to get a loan from the bank for $5,000. When counting all their money they add in -$5.000 to show they still owe the bank.
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14. Solve the problems on Part A of your worksheet now. Click to the next slide when done.
20. One Way to Add Integers Is With a Number Line When the number is positive, count to the right. When the number is negative, count to the left. + - 0 1 2 3 4 5 6 -1 -2 -3 -4 -5 -6
21. One Way to Add Integers Is With a Number Line + - +3 + -5 = -2 0 1 2 3 4 5 6 -1 -2 -3 -4 -5 -6
22. One Way to Add Integers Is With a Number Line + - +6 + -4 = +2 0 1 2 3 4 5 6 -1 -2 -3 -4 -5 -6
23. One Way to Add Integers Is With a Number Line + - +3 + -7 = -4 0 1 2 3 4 5 6 -1 -2 -3 -4 -5 -6
24. One Way to Add Integers Is With a Number Line - + -3 + +7 = +4 0 1 2 3 4 5 6 -1 -2 -3 -4 -5 -6
25. Integer Subtraction Rule Subtracting a negative number is the same as adding a positive. Change the signs and add. 2 – (-7) is the same as 2 + (+7) 2 + 7 = 9!
26. Here are some more examples. 12 – (-8) 12 + (+8) 12 + 8 = 20 -3 – (-11) -3 + (+11) -3 + 11 = 8
27. Solve the problems on Part C of your worksheet now. Click to the next slide when done.
29. How do we know that “ Subtracting a negative number is the same as adding a positive” is true? We can use the same method we use to check our answers when we subtract.
30. Suppose you subtract a – b and it equals c: a – b = c 5 – 2 = 3 To check if your answer is correct, add b and c: a = b + c 5 = 2 + 3
31. Here are some examples: a – b = c a = b + c 9 – 5 = 4 9 = 5 + 4 a – b = c a = b + c 20 – 3 = 17 20 = 3 + 17
32. If the method for checking subtraction works, it should also work for subtracting negative numbers.
33. If a – b = c , and…. 2 – (-5) is the same as 2 + (+5) , which equals 7 , Then let’s check with the negative numbers to see if it’s true…
34. a – b = c a = b + c 2 – (-5) = 7 2 = -5 + 7 It works! a – b = c a = b + c -11 – (-3) = -8 -11 = -3 + -8 YES!
35. Solve the problems on Part D of your worksheet now. Click to the next slide when done.
36. Check Your Answers 1. Solve: 3 – 10 = 7 Check: 3 = 10 + (-7) 2. Solve: 17 – ( 12) = 29 Continued on next slide Check: 17 = -12 + 29
38. You have learned lots of things About adding and subtracting Integers. Let’s review!
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41. One Way to Add Integers Is With a Number Line When the number is positive, count to the right. When the number is negative, count to the left. + - 0 1 2 3 4 5 6 -1 -2 -3 -4 -5 -6
42. Integer Subtraction Rule Subtracting a negative number is the same as adding a positive. Change the signs and add. 2 – (-7) is the same as 2 + (+7) 2 + 7 = 9!
43. How do we know that “ Subtracting a negative number is the same as adding a positive” is true? We can use the same method we use to check our answers when we subtract.
44. a – b = c a = b + c 2 – (-5) = 7 2 = -5 + 7 It works! a – b = c a = b + c -11 – (-3) = -8 -11 = -3 + -8 YES!
45. Discuss with a partner ways that you know that that is problem is solved correctly. 6 – (-9) = 15
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