Sunday, October 30, 2011

Fun Algebra with Kids

Well... Halloween is usually the time that I introduce algebra a little bit. I tell the students that one number in our number sentence is wearing his Halloween costume (usually I draw a little ghostie). What we have to figure out is, what is the ghostie number?

For example: 3 + 7 = ghost + 2

This requires a clarification of what "=" actually means (an important prerequisite for algebra later on). A child who thinks = means "put the answer here" will say that the ghostie number is 10. 3 + 7 = 10. They will ignore the + 2 since they have no idea how to process it. One of the teachers in my evening class was saying that they have stopped using the word "equal" at her school and instead they say "is the same as." 3 + 7 IS THE SAME AS 8 + 2.

I wanted this to be a fun project for the kids so I am thinking about using rubber stamps to be the variables and making a book of Halloween math problems that they can take home. We will use a simple sheet of 8 1/2 x 11 card stock, so the book is sturdy. Lie a ruler down at the top edge of your paper (lay it landscape or portrait, whichever you prefer). Draw a line at the bottom edge of the ruler, remove the ruler, and cut the strip of paper you have traced off of your big sheet. You now have a slightly truncated original sheet and a strip of paper. Decide where on your big paper your math problem will go and lay the ruler down again across the paper in that spot. Trace the top edge and the bottom edge of the ruler (this is where the strip of paper will fit later). Now, write your math problem with the correct answers in all parts of the problem. Write it inside the lines you have traced and it's best if you write it big! You can make it as complicated or as simple as you want but there can only be one variable (one number which is hidden by a ghostie). Next, choose which number you are going to hide. Lay the short edge of the ruler on either side of this number and draw a line so that you have put this number in a little box. Fold your paper and cut out the left and right lines on either side of your number. It should have little slits on either side, so that the paper strip can be run through the large piece of paper, first covering and then revealing the hidden number. Thread your strip through the large piece of paper using the slits to align it over the number you wish to hide. Use a rubber stamp, or draw a picture if you prefer, to "hide" the number with his Halloween costume. Quiz a friend -- can they guess the hidden number? Pull aside the paper strip to find the correct answer. Add more problems to the sheet if you wish.

This will be a fun activity for the end of the day on Monday. And then for the rest of the week I can write ghostie problems on the board to start our day. But I want it to be a really concrete concept -- the idea that the variable is a hidden number which you want to figure out, in order to make the statement be true.

P.S. I just tried this concept out on Leah and she loved making it. It's nice that they have to think of a complete equation in advance and then decide what the variable will be -- so they are solving their own problems first before I ask them to solve one of mine. She carefully drew a little witch on her slip of paper to be the costume, but the nice thing about using rubber stamps as variables is that the children who want to keep doing more of this during the year can just get out the box of rubber stamps and make problems for a friend to solve. They can do this ad infinitum.

3 - flower = 0 + 2

flower = ?

1 comment:

Rhoda said...

A nice place to go from here might be Incredible Equations. Look for the original NCTM article in Teaching Children Mathematics, or some of the follow up materials that have sprung up online: