Download Adding Integers

Unit 1: Integers

There are two types of problems:
 1- When the signs are the same
 3+2=5
 -3 + -2 = -5
 2- When the signs are different
 3 + -2 = 1
 -3 + 2 = -1


Same signs?
Add them together, keep the same sign.
3 + 2 =5
Here, both numbers are positive. So, we just add the
two numbers, and keep the answer positive.
-3 + -2 = -5
Here, both numbers are negative; so, we just add
the two numbers, and keep the answer negative.

Different signs?

Subtract the numbers, take the sign of the bigger
number.
3 + -2 = 1
First, we subtract 3-2 and get 1. The bigger number is 3
and it is positive, so our answer must be positive.
-3 + 2 = -1
We know that 3-2 gives us 1. The bigger number is 3 and it is
negative, so our answer must be negative.
**When I say “bigger number” I mean the sign with the greater absolute value**
Complete these four problems, then click the mouse for the answers.
-20
-10 + -10 = ______
-5
-10 + 5 = ______
+5
6 + -1 = ______
+20
15 + 5 = ______
Since both numbers have the same sign, we
add them together, and keep the same sign.
10+10=20, and they are both negative, so our
answer is -20
Both numbers have a different sign. Therefore we
subtract: 10 – 5 = 5. Since 10 is bigger than 5, we
keep the sign from 10, which is negative.
Both numbers have different signs, so we have
to subtract: 6-1=5. The bigger number is 6 and
it’s positive, so our answer is positive.
Both numbers have the same sign, so we add
them together: 15 + 5 =20. Since both numbers
are positive, our answer must be positive.

Need more help? Try this technique
-8 + 5 = _______
We have a negative 8 and a
positive 5, let’s draw this out:
Next, for every positive we
have, let’s take away a
negative…
Finally, we see that we only
have 3 left in the negative box;
so our answer must be -3
Negative
-8
Positive
+5

Another technique is to draw a number line:
-8 + 5 = _______
---I-----I-----I-----I-----I-----I-----I-----I-----I-----I-----I------I------I------I------I------I----
-8 -7 -6 -5 -4 -3 -2 -1 0
1 2
3
4 5
6
7
Start by tracing back to -8
Then, from -8, trace forward +5
So our answer must be -3

That’s it! Here are some more practice
problems to try…
-2
-10 + 8 = ____
2
8 + -6 = ____
12
5 + 7 = ____
-6
4 +-10 = ____
-3
7 + -10 = ____
0
-5 + 5 = ____
-10
-6 + -4 = ____
-10
-5 + -5 = ____

This has been a Rockin’ Presentation by:
Mr. Lattyak