Subtracting Integers

We saved subtracting until the very end! The kids have mastered multiplying and dividing, are getting there on adding, and today we completed the puzzle with subtracting integers. We worked through the four different kinds of subtracting integer problems (listed below) and talked through how to solve them. The two tricky things involved imagining a number line in our heads for normal subtracting, and then when we got into the minus a negative (ie. 3 - -9) that really means we're adding. I know! So confusing! Here's the four kinds:

-1 - 4 = -5
1 - 4 = -3
-1 - -4 = 3
1 - -4 = 5

Got it? Ha!

Tonight I did ask them to complete #s 1-11 on a Subtracting Integers Sheet... but here are the problems with the answers...

1. 5 - (-10) = 15
2. -4 - (-10) = 6
3. -4 - 1 = -5
4. 3 - (3) = 0
5. -7 - (-7) = 0
6. -5 - (-8) = 3
7. -7 - (-6) = -1
8. 7 - (-15) = 22
9. 8 - (-9) = 17
10. -6 - (-8) = 2
11. -1 - 8 = -9

If they don't seem to be getting it just yet, no worries. This is hard! And abstract! Tell them we'll figure it out. :)