3.4+“Undoing”+with+Addition+And+Subtraction

20-Arpril -2009 SF Big Idea Negative numbers help us to model many real world situations. Investigation 3: Subtracting Integers Essential Question #3: How do I find the difference between integers? **Notes:**None



-17+13= -4
 * A1. Complte the addition sentence -17+13=?.**

4-(-13)=+17
 * A2. Write a subtraction sentence that " Undoes " the addition sentence you found in pat 1.

B1. Complete the addition sentence -4+-18=?. -4+(-8)= -22

B2. Write a subtraction sentence that " undoes " the addition sentence you found in part 1. 22-4= 18

C. Write a subtraction subtraction that solves each problem. 1. ?+-18=** **6** ?=24 **Subtraction Sentence:** 24-6=18
 * 2. ?+-13=-41** ?=-28 **Subtuaraction Sentence:** -28-(-41)=13
 * 3. ?+6.1=-3.2** ?=-9.3 **Subtraction Sentence:** 3.2-9.3=-6.1
 * 4. ?+negative one third=** **one third** ?=two third **Subtraction Sentence:** one third + one third = two thirds

1. ?-(-6)=-6** ?= 0 **Addition Sentence:** 0+(-6)=-6
 * D. Write an addition sentence that solves each problem.
 * 2. ?-(-2)=3** ?=1 **Addition Sentence:** -1+3=2
 * 3. ?-5.3=-7.1** ?=-1.8 **Addition Sentence:** 7.1+(-5.3)=1.8
 * 4. ?- negative one fourth= negative three fourths** ?=-1 **Addition Sentence:** -one fourths - negative three fourths = -1


 * __Follow up__

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

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

3.8-1.2=2.6
 * 2b. Write a subtraction sentence.

-11-6=-17
 * 3a. Complete the subtraction sentence -11-6=?.

-17+6=-11
 * 3b. Write a addition sentence.

Yes, because it depends on the integers and their signs. Eg. 11-5=6 & -8-(+3)=-11 ** ** **  **  **    **
 * 4. When you add positive and negative integers, sometimes you get a positive sum and sometimes you get a negative sum. Is this same true when you subtract positive and negative integers?
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