Teaching Algebra with Manipulatives

Using Overhead Manipulatives
(Use with Algebra 1, Lesson 1-5)
The Distributive Property
Objective Use a geometric model of the Distributive Property to simplify
expressions.
Materials
• centimeter grid paper transparency*
• overhead area tiles*
• transparency pen*
• blank transparencies * available in Overhead Manipulative Resources
Algebra 1—Chapter 1
Demonstration 1
Using Area to Demonstrate the Distributive Property
• Remind students that the area of a rectangle is the
product of its length and width. On the centimeter
grid paper, draw a 9 14 rectangle and label the
length and width. Ask students how to find the area
of the rectangle. 9 14 126
14
9
• Draw a dashed line separating the length into
sections of 10 and 4 units. Label each section. Ask
students how they can use the two rectangles to find
the area of the 9 14 rectangle. Find 9 4 and 9
10 and add them: 36 90 126.
• Below the rectangle, write the equation
9 (10 4) (9 10) (9 4).
Ask students what the models shows. Sample
answer: When you multiply a number times a sum
the result is the sum of the products of the number
and each part being added.
14
9
10
4
9 (10 4) (9 10) (9 4)
• Use a blank transparency to trace the 9 14
rectangle and dashed line. Also include the 9, 10, and
4 labels. Then change the 9, 10, and 4 labels to a, b,
and c. Ask students to restate the equation using the
variables. a(b c) a b a c or a(b c)
ab ac
b c
a
(continued on the next page)
b
c
© Glencoe/McGraw-Hill 31 Teaching Algebra with Manipulatives