3.4+Undoing+with+Addition+and+Subtraction

​ ​ 04/24/10 SC

. Big Idea Negative numbers help us to model real world situations. Investigation 3: Subtracting integers Essential question #3: How do I find the difference between integers? =A.= 1. Complete the addition sentence -17+13=? -17+13=4 2. Write a subtraction sentence that "undoes" the addition sentence you found in part 1. 4-(-13)=17

1.Complete the addition sentence -4+-18=? -4+(-18)=-22 2. Write a subtraction sentence that "undoes" the addition sentence you found in part 1. 22-4=18
 * B.**

1. ?+-18=6(?=24) 24-6=18 2. ?+-13=-41 (?=-28) -28-(-41)=13 3. ?+6.1=-3.2 (?=-9.3) 3.2-9.3=-6.1 4. ?+(-1/3)=1/3 (?=2/3) 1/3-(-1/3)=2/3
 * C.** Write a subtraction sentence that solves each problem.

1. ?-(-6)=-6 (?=0) 0+(-6)=-6 2. ?-(-2)=3 (?=1) -1+3=2 3. ?-5.3=-7.1 (?=1.8) 7.1+(-5.3)=1.8 4. ?-(-1/4)=-3/4(?=-1)Write a subtraction sentence that is related to the addition sentence you found in part a. -2.6-3.8=
 * D.** Write an addition sentence that solves each problem.

-3/4+(-1/4)=-1

Follow up 1. Can you write a different subtraction sentence to go with 3+11=14? 14-11=3

2. a. Complete the addition sentence 3.8+(-2.6)=? 3.8+(-2.6)=1.2

b. Write a subtraction sentence that is related to the addition sentence you found in part a. 3.8-​1.2=2.6

3. a. Complete the subtraction sentence -11-6=? -11-6=-17 b. Write a addition sentence that is related to the subtraction sentence you found in part a. -17+6=-11

4. When you add positive and negative integers, sometimes you get a positive sum and sometimes you get a negative sum. Is the same true when you subtract positive and negative integers? Explain. Yes, because it depends wich integer has more of a larger absolute value and if it is a positive and negative integer.