Saturday, August 31, 2013

Exponent Rules GAME

I've posted on this topic a bunch of times here, here and here, but I'm not tired yet of hammering more nails into this coffin.  I think that correctly mastering exponent rules is a gateway skill.  Maybe one of the most important gateway skills in algebra.  Exponent rules:

  • Formalize the meaning of multiplication and division for algebra.
  • Provide the first forum for students to effectively use reducing in an algebraic context.
  • Introduces students for the first time to how simple algebra definitions (i.e. the definition of an exponent) can be used to prove a multitude of other cool rules that make doing math easier.  In other words exponent rules formalize the structure of mathematical logic and proof for students.
  • Is often the first time students see and manipulate algebraic rules represented purely with variables.  If students can understand and use exponent rules, it prepares them for using and understanding other rules represented with abstract mathematical language. 
  • Set the foundation for a student's understanding of polynomial functions, radical functions, exponential functions, and logarithmic functions.  Without a solid understanding of exponents and their properties students will struggle with all of these types of functions later.
And I think we can teach the exponent rules well because they're just not that hard to derive, but the level of abstraction is what makes it difficult for students.  So in teaching exponent rules, I believe we should focus on teaching students the abstraction, and the rules get learned along the way.  

That being said, I don't know how to do it but I keep trying.  I've updated my lesson on developing the exponent rules.  You can find that here and also, I've developed a simple game that I hope helps students cement the rules and learn to play with them.  The game involves both strategy, luck and understanding of exponents so I think it's pretty good but it's only had a few trial runs.

Materials: You'll need a set of blue cards and a set of green cards.  You can download the cards and the rules here.  Lay the cards out like so:

Object: Combine your starting expression with green cards to create the target expression.

(1) You may use as many green cards as you wish.
(2) Cards that look like this: (   )^2 must be applied to your whole expression so far.  So if you start with the card “ab" and you grab the green card (   )^2  you will end up with a^2 b^2
(3) If neither player can find the right cards to create the target expression, three more green cards can be put down. 
(4) Once the target expression is reached by a player, that player gets the blue card and all the green cards they used to make the winning expression.  A new blue card is then put down and green cards are added until there are 9 green cards again.
(5) Once all the green cards are gone, the game is ended and the player with the most green and blue cards wins.

Here are several examples of how the players in the set-up above could reach the target expression. 

Saturday, August 3, 2013

Not Ratios again!

Students either seem to "get" ratios or they don't.  I don't know what to do about it.  I made a really detailed ratio and proportion lesson based on beats per minute and the fastest guitar player in the world for my algebra 1 students.  3 students that I used it on loved it and understood everything just fine, 1 student could not get it no matter what I tried.

I drew a picture of a person and said that he was 6 ft tall but a shrink-ray shrunk him to 2 ft.  If his legs were 3 ft long originally how long are they now?  My student thought for a second and then said "-1 feet?"  I tried pictures of triangles, I tried explaining that scale factors worked with multiplication and division, not addition and subtraction, I tried just showing him the math steps based on fractions in a last ditch attempt to get him to walk out of the class with something.  But none of it worked because he didn't have an internal sense for proportion.  He could do the mechanism of cross-multiplication, but a "sense" for proportion just eluded him.

I'm now working on a lesson for geometry introducing ratio and proportion and I'm getting a little cold and clammy because I have nothing.  My experience is just kids see it or they don't and if they don't, I don't know what to do.  Sheer perseverance and drill have helped these students eventually reach an "aha" moment, but it just seems to be based on time, not on cleverness of the activity (or I haven't found or thought of a sufficiently clever activity.)  I've been sitting in a coffee shop for an hour now and so far, I just have a warm-up:

  1. Which pair of numbers is out of place?  Explain why you chose that pair.
    1.    3 and 4
    2.  5 and 6
    3.  9 and 12
    4.   27 and 36
  2. Which pair of numbers is out of place?  Explain why you chose that pair.
    1.    9 and 12
    2.   12 and 15
    3.   20 and 25
    4.   32 and 40
  3. You got a part time job at The Pizza Hub.  You just found out that your co-worker makes more money.  Which statement would make you angrier?  Why?
    1.    Your coworker makes $10 more than you.
    2. Your coworker makes double what you make. 
 If there's anything out there to follow this warm up with, I'd love to hear about it.

Update [8/4/2013]  Here's the lesson I eventually came up with.  I think it does a decent job.  

And here's an "I notice, I wonder" activity that could be used to get students thinking about ratio and proportion.  Both of these are PDFs to preserve formatting, but if you go to my scribd profile you can find the .docx versions.