Teaching Algebra with Manipulatives

Using Overhead Manipulatives
(Use with Algebra 1, Lesson 5-1)
Find the Slope of a Line
Objective Find the slope of a line.
Materials
• coordinate grid transparency*
• transparency pens*
• straightedge*
• blank transparencies
* available in Overhead Manipulative Resources
Demonstration 1
Finding Slope: Positive, Negative
• At the right, copy Graph 1 on the coordinate grid transparency.
• Tell students that slope is defined as
or r ise
.
change in x run
Ask them what the rise and run are for this line. (3; 2) Ask
why the values are both positive. Movements up and right
are denoted by positive numbers; movements down and left
are denoted by negative numbers.
• Ask students to find the slope of the line. 3 2
• Ask whether moving up 3 units and right 2 units from (3, 5)
will result in a point on the line. yes
• Graph and label the points C(0, 0) and D(1, 4) on the second
coordinate grid. Draw the line determined by the points.
• Ask students to find the rise and run for the line in graph 2.
4; 1
“What is the slope of the line?” 4 1 or 4
• Ask, “Does it matter which point is used first when finding
slope?” no, as long as its coordinates are used first to
calculate both rise and run
0 (4)
• Write 4 1 4 and 4 0
4
4 beside the grid
1 0 1
to show students this is true.
0 (1)
change in y
y
B
A
O
Graph 1
y
O C
D
Graph 2
x
x
© Glencoe/McGraw-Hill 96 Teaching Algebra with Manipulatives