Learning Target: I can add signed integers.


 

Adding Integers


The sums of integers can be placed in two categories: adding integers with the same signs (both positive or both negative) and adding integers with different signs (one positive and one negative).  Different rules apply depending on whether the addends have the same sign or not.


Same signs

Add the absolute values of the numbers.  Then attach the sign of the addends.

 

Different Signs

Subtract the number with the smaller absolute value from the number with the larger absolute value. Then attach the sign of the addend with the larger absolute value.


You can show the addition of signed numbers on a number line.

Example 1

3 + (−5)


3 + (−5) = −2



Notice how the addition of opposite numbers results in zero.

Example 2

−4 + 4


−4 + 4 = 0



Example 3

Add:  5 + (−12)

|5| = 5;  |−12| = 12
12 − 5 = 7
because |−12| > |5|, attach the negative sign.


5 + (−12) = −7



Let's Practice Together

Add each.

1.)  4 + (−8)


2.)  12 + (−17) + (−18)



Your Turn

3.)  −6 + 7


4.)  −651 + (−231) + 524


5.)  −92 + (−79)


6.)  36 + 29 + (−65)

 



Check for Understanding

1.)  A golfer's score on his first five holes are −2, +1, −2, −1, and +3.  What is his total score so far?























Answers
1.)  -4
2.)  -23
3.)  1
4.)  -358
5.)  -171
6.)  0
Check for Understanding
1.)  -1