Intermath | Workshop Support

 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

Restate the problem in your own words. Discuss mathematical similarities between this problem and other problems you have solved.

Plans to Solve/Investigate the Problem

Create an equation based on the way the problem is written (order of stipulations) and a spreadsheet to support/solve the problem.

Investigation/Exploration of the Problem

Equation where n=number

n+129= 2(129-n)

n+129=258-2n

3n=129

n=43

 Double Trouble N N+129 129-N 2(129-N) 50 179 79 158 49 178 80 160 48 177 81 162 47 176 82 164 46 175 83 166 45 174 84 168 44 173 85 170 43 172 86 172

Extensions of the Problem
The problem can be further explored by writing the equation as follows:

n+129=2(n-129)

n+129=2n-258

387=n

387+129=2(387-129)

516=2(258)

516=516

Discussion and examination of the order of stipulations will eliminate this equation as a possibility (add to and subtract from).

Author & Contact
Susan Kelly
mailto:skelly@rockdale.k12.ga.us

Link(s) to resources, references, lesson plans, and/or other materials