Download AddingPosAndNegNumbers - Dynamic Math Institute

You will need two colored pencils or markers to get started
Example 1) How would you add 4 + 3 using a number line?
-10
-9
-8
-7
-5
-6
-4
-3
-2
-1
2
1
0
4
3
5
6
7
9
8
10
Example 2) How could you add –5 + -2 using a number line?
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
-2
-1
0
1
2
3
4
5
6
7
8
9
10
Example 3) What is –4 + 9?
-10
-9
-8
-7
-6
-5
-4
-3
Now that we have practiced, let’s use the computer to help us make
some conclusions about adding positive and negative numbers
Adding Positive and Negative Numbers
Using Geometer Sketchpad
Name __________________
1. Turn on the computer and Hit Start, Programs. Look for GSP 4.02.
Click on the ICON to open. Make sure that you maximize your screen
2. Open the sketch called “Add Integers.gsp”
This sketch is for use with the activity
Adding
Integers, which
starts 7
on + 5.
3. Look at the first
problem
given
page 32 of Teaching Mathematics.
7
+
-5
5
0
drag
What is the answer?
drag
5
10
15
20
Q1: How can you figure out the answer using the blue and green
arrowsscale
on the number line?
Q2: Which direction (positive or negative) is each arrow on the
number line moving?
Please finish the first rule we need to KNOW
about adding Numbers:
Positive Number + Positive Number =
 Go ahead and change the problem to –4 + -2, by moving each drag button
above the number. What is the answer?
Go ahead and try the following problems and put the answer in the blank:
-9 + -8
-3 + -15
-7 + -14
Q3: Which direction (positive or negative) is each arrow on the
number line moving?
Q4: Based on your answer in Q3, what is the only type of answer
(negative or positive) you can get if you add two negative numbers
together?
Please finish the Second rule we need to KNOW
about adding Numbers:
Negative Number + Negative Number =
STOP
Please get teacher signature before proceeding ____________
 Change the problem to 9 + -9. What is the answer?
Go ahead and try the problems, using the computer. Put the answers
in the blank:
-4 + 4
4 + -4
-4 + -4
Q5: What must be true about two numbers if their sum is zero?
Please finish the Third rule we need to KNOW
about adding Numbers:
The sum of any number and
always zero.
is
 Calculate 4 + -7 using the software. What’s the answer?
Go ahead and try the problems, using the computer. Put the answers in the
blank:
-4 + 7
10+ -2
-14 + 8
Q6: When adding a positive and negative number, how can you tell if
the answer will be negative or positive?
Please finish the FINAL rule we need to KNOW
about adding Numbers:
the sum of a negative number and a positive
number is
, if the positive
number is larger, and ______________________, if the
negative number is larger
(Larger here means farther from zero).
Before we get started with some problems, could you please answer the
following question: Why does adding a positive and a negative number
seem more like subtracting?
Now that you know the rules, go ahead and do the following problems.
If you need a number line, please use the following number line below:
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
1. 9 + 1
2. -6 + 6
3. -5 + (-1)
4. -6 + (-6)
5. 0 + (-4)
6. 3 + (-8)
7. 6 + (-10)
8. -3 + 8
4
5
6
7
8
9
10