Adding & Subtracting Integers

Adding & Subtracting Integers

Adding Positive Numbers To understand adding positive and negative numbers we will look at what happens at my ICE CREAM STORE. I have 3 ice cream cones ready And then I make 4 more… 4 3 When I have positive numbers (ice cream cones) and I want to find the total amount , I count them together. My total is 7. I could write this as a number sentence 3 + 4 = 7

Adding Negative Numbers Here come the Ice Cream Gobblers. Ice Cream Gobblers take our ice cream cones, so we will represent them with negative numbers. A few minutes later, more Ice Cream Gobblers arrive. First to arrive are these Ice Cream Gobblers. -2 -3 When I have two groups of negative numbers (Gobblers) and I want to find the total amount, I count them together just as I did with the two groups of positive numbers. My total is -5. I could write this as a number sentence -2 + (-3) = -5

Adding Positive and Negative Numbers This morning in my Ice Cream Store, I have ready 4 ice cream cones. Here are my ice cream cones. A few minutes later, 3 Gobblers arrive. -3 4 When I am adding two groups that are different, like my positive cones and my negative Gobblers, I have to watch out. The Gobblers will eat the cones. To find out what happens when I put these groups together I look to see which group is bigger. In this case the cones have a bigger amount (4), than the Gobblers (3). Since the bigger amount is 4 and it is positive my final total will be positive. Three Gobblers will eat 3 of my cones so I will only have one left. I could write this as a number sentence 4 + (-3) = 1

Adding Positive and Negative Numbers Yesterday morning in my Ice Cream Store, I had ready 2 ice cream cones. Here are my ice cream cones. 4 Gobblers came in. -4 2 To find out what happens when I put these different groups together I look to see which group is bigger. In this case the gobblers have a bigger amount (4), than the cones (2). Since the bigger amount is 4 and it is negative my final total will be negative. Two Gobblers will eat 2 of my cones and 2 Gobblers will be hungry. I could write this as a number sentence 2 + (-4) = -2

Practice Adding Signed Numbers 2 + 1 = 3 Check your answer -2 + (-2) = -4 Check your answer 2 + (-1) = 1 Check your answer Check your answer -5 -2 + (-3) = -3 + 2 = -1 Check your answer -5 + (-1) = -6 Check your answer

Subtracting Positive Numbers Today in my Ice Cream Store, I had ready 5 ice cream cones on the counter. 2 5 My friend Jennie came in to visit and knocked 2 of my ice cream cones onto the floor. Since Jennie has ruined them, I will need to subtract them from my inventory. I could write this as a number sentence 5 - 2 = 3

Subtracting Negative Numbers This is the operation where most of the confusion lies. When we subtract negative numbers it is the same as adding. -2 +1 -1 Here comes Gobbler Josh, he doesn’t like vanilla so he’s bringing his ice cream back. Let’s look at my Gobblers. I have two Gobblers at my counter. Subtracting a negative Gobbler, means I’m adding a cone. If I give this cone to one of the Gobblers waiting at the counter. I would only have one Gobbler left. My number sentence starts like this -2 – (-1) = -1 But when we subtract a negative we change the - - to a + -2 +1 = -1

Subtracting Negative Numbers My number sentence starts like this -2 1 = -1 When two negatives get together they always change to a positive!

Practice Subtracting Signed Numbers 2 - 1 = 1 Check your answer -2 - (-2) = 0 Check your answer 2 - (-1) = 3 Check your answer Check your answer -2 - (-3) = 1 -3 - 2 = -5 Check your answer -5 - (-1) = -4 Check your answer

Practice Adding and Subtracting Signed Numbers -3 + -2 = -5 Check your answer -8 + 5 = -3 Check your answer 400 + (-200) = 200 Check your answer Check your answer -2 - 7 = -9 4 – (- 2 ) = 6 Check your answer -500 - 325 = -825 Check your answer

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Adding & Subtracting Integers