Elementary Algebra

This blog is dedicated to the special education math class at Catalina Foothills High School and the 5th grade class at a local charter school.  Some of these concepts are kind of tricky at first.  I’d like BDLbiochem to be about helping kids make that first intuitive leap.

What is algebra?

Algebra differs from adding, subtracting, multiplying, and dividing numbers because letters come in to represent unknown numbers.

An example of an unknown?

Tom and Mike were eating lunch and watching girls.  Today’s lunch was hamburgers and potato chips.   Tom opened his bag of potato chips just as Jill walked by.  Tom turned his head to watch Jill.  Mike ate 20 of Tom’s potato chips.  “Ha, ha!  I just ate 20 of your chips!,” said Mike.

What is an expression to describe what just happened?

Tom never bothered counting his chips.  We will use the letter y in place of the unknown number of chips that Tom had in his bag before Mike took 20.

An expression has numbers and letters in place of numbers that we do not know

Tom decided to count the chips he had left.  Only 10 are left.  How many chips did Tom have before Mike ate 20?

What is an equation?

In this particular case an equation says that the unknown number of chips that Tom started with (y) minus the 20 that Mike ate is equal to the number of chips left in the bag (x).

An equation says that two different expressions are the same thing.

Tom counts the number he has left in the bag.  Often we use “x” to identify unknown numbers that we can measure.  In our case Tom  measured “x” by counting the potato chips left in the bag.


The “=” sign means we must do the same thing to both sides.  In this case we  “solved for y.”



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