3.2+Subtracting+on+a+Number+Line

4-5-09 F.H.

Big Idea: Negative numbers help us to model many real world situations.

Essential Question: How do I find the difference between integers?

1)** +7-+9= -3
 * A)Use the number line to find each difference. Use a chipboard to check your work.
 * 2)** -7-+9= -16
 * 3)** +7--9= 16
 * 4)** -7--9= 3

1)** +12-+3= 8
 * B)Use a number line to find each sum or difference.
 * 2** +12+-3= 15
 * 3)**-10--7=-17
 * 4)**-10++7= -17

My two sentences are 5+-2=3 and -2+5=3.
 * C) Find the difference between each pair of numbers on a number line. In each case, tell how the distance is related to the difference is related to the difference between the two numbers.**
 * 1)** 1 and 5 are positive numbers so we only count on the right side of the number line**//,//** we move 4 spaces.
 * 2)** -1 and 5 are positive and negative numbers so we move on both sides of the number line, so there are extra spaces, we have to move 6 spaces.
 * 3)**-5 and -9 are both are both negative numbers, so we stay on on the left side of the number line, we move 4 spaces.
 * 4)** -3 and 3 are both negative and positive numbers, so we go on both sides of the number line, we move 6 spaces.
 * D) Write two number sentences illustrated by this figure.**

**3.2 Follow Up 1)** **When you add two positive integers you get a positive sum . When you subtract two positive integers, do you always get a positive difference? Explain.**

No you can't get a negative number if you subtract a greater number from a smaller number, because if your subtracting more from a number than it is you go below 0 which is negative.


 * 2) When you use the number line model, you can think of the //absolute value// of a number as its distance from 0. For example, 3 and -3 are each 3 units from 0, so the absolute value of each number is 3.**


 * Use a number line to help you find a pair of numbers with the given absolute value.**


 * A)** 10 and -10
 * B)** 5 and -5
 * C)** 1 and -1
 * D)** 7 and -7