Math = Love: Solving Equations with Variables on Both Sides of the Equal Sign

## Saturday, October 24, 2015

### Solving Equations with Variables on Both Sides of the Equal Sign

After solving equations with variables on one side of the equal sign, it's time to do variables on BOTH sides of the equal sign.

For this topic, I made a booklet foldable with two word problem practice problems inside.

Outside of foldable with steps:

Inside:

Every year when we are reviewing for the EOI exam, my students get hung up on this released test question:

Usually, once I help them set up the revenue = costs equation, they can figure it out.  I decided to write some of my own practice problems about this and stick them in this unit so students could start getting used to this sort of problem.

For the two problems I wrote to make sense, there's a few facts you have to know.

1.  Drumright, the town I live in and teach in, is a former oil boomtown.  We like to theme everything around oil.  Our yearly festival is called Oil Patch.  Our newspaper is called the Gusher.  We have a motel in town called the Boomtown Inn.

2.  I taught this lesson on the Monday AFTER Oil Patch.  I'm part of the Friends of the Library organization, and our fundraiser at the festival was to sell bookmarks designed by local elementary school students and cotton candy.  (Except the cotton candy machine wasn't working properly so I just ended up selling bookmarks...)

 Last Year's Oil Patch Setup

3.  Booth Rental is \$50.  I just made up all the other numbers.  Don't worry.  I told my students this, too.

I like that students had to write their own costs and revenue equations before being able to move forward.  This made the question of even a higher level of difficulty than what will be expected on the EOI.

I really liked it when one student suggested that I would need to sell 50 bags of cotton candy to break even.  This sparked a debate with other students in the class who pointed out you also had to pay for supplies for the cotton candy you sell!

After working through these two word problems, I gave my students some more traditional practice problems with variables on both sides of the equal sign.

And, just like with solving equations with variables on one side of the equal sign, I had students use the calculator to check the solutions they found.

They still used the calculator's store function, but they had to enter both sides of the equation and see if the answers matched.