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 Write-up

Title
DOUBLE TROUBLE

Problem Statement
What number can you add to 129 and subtract from 129 such that the sum of the number and 129 is twice the difference between 129 and the number?

Problem setup

What number can be added to 129 and subtracted from 129 such that the sum of the number and 129 is the same as twice the difference of 129 and the number?

Plans to Solve/Investigate the Problem

Set up and solve an algebraic equation that meets the criteria posed in the problem.

Investigation/Exploration of the Problem

1.      Let n represent the number.

2.      Let n + 129 represent the sum of the numbers.

3.      Let 129 – n represent the difference of the numbers.

4.      Let n + 129 = 2(129 – n) represent the sum of the number and 129 is twice the difference between 129 and the number.

5.      Solve the equation:        n + 129 = 2(129 – n)

n + 129 = 258 – 2n

n + 129 + 2n = 258 -2n +2n

3n + 129 = 258

3n + 129 -129 = 258 -129

3n = 129

3        3

n = 43

6.  Check the solution by substituting it into the original problem:       43 + 129 = 2(129 – 43)

43 + 129 = 2(86)

43 + 129 = 172

172 = 172

Author & Contact
Insert name and contact information.
lparsons@rockdale.k12.ga.us

Link(s) to resources, references, lesson plans, and/or other materials
Lucky Find
Mystery Number