Today I had a discussion on how to introduce the basic concept of variables in math using real life examples. We came up with ideas of using boxes containing matches, or M&Ms representing the variables and little piles of the actual items so e.g. 4 boxes with 2 M&Ms would equal a small pile of M&Ms. Problems of giving candy to kids aside, is that a proper way to introduce the concept of a variable? Are there better real life examples which they can perform at school?
Do you have any ideas how to teach this to 13 year olds with a very mixed performance in school (really slow ones to some fast learners).