Teaching Algebra with Manipulatives

Using Overhead Manipulatives
Demonstration 1
Solve Equations by Addition (Continued)
• Clear the mat and blank transparency. Place 1 cup and
3 positive counters on the left side of the mat and 8
negative counters on the right side of the mat. Ask
students what equation is represented. x 3 8
Write the equation (and the subsequent steps) below
the mat.
• Ask students what you should do to each side to be
able to remove all counters from the left side. Add
3 negative counters, or 3, to each side. Add the
counters, and then remove the zero pairs. Ask students
to state the solution. 11
• Clear the mat and the blank transparency. Write the
equation x 2 5 below the mat. Ask students how
they might use the counters to show this equation. If
necessary, remind them that to subtract an integer, you
add its opposite. 1 cup and 2 negative counters on the
left, 5 positive counters on the right
Model the equation.
• Ask them what to do to each side to isolate the cup on
one side. Add 2 positive counters to each side Add the
counters, then remove the zero pairs. Ask students to
state the solution. 7
• Ask students how to model and solve the equation
x 4 8. Place 1 cup and 4 negative counters on
the left side and 8 negative counters on the right side.
Add 4 positive counters to each side. Remove the zero
pairs. The solution is 4. Have them draw each step as
you model it.
Algebra 1—Chapter 3
• Ask students to show the check of the solution of
x 4 8. 4 4 8
(continued on the next page)
© Glencoe/McGraw-Hill 61 Teaching Algebra with Manipulatives