At 16 when applying for my driving permit, I just knew that by the time I got my license, I'd be 5 feet 5 inches tall. Five had always been one of my favorite numbers, so how could it not happen? As it turned out, by 16 I was done growing. Once I came to terms with this sad fact, it became a great story to tell to introduce functions.
"Can I be 5'4" and 5'5" at the same time?" My students always give me a, "seriously, this is Math?" face when I ask this question. I mean, obviously not! Vertical lines are not functions because they make no sense in real life! So then I draw 2 graphs on the board and asking students which of the two could possibly happen in real life:
I'm 4 feet, 5 feet and 6 feet tall when I'm 16 years old.
Every student knows which one "makes sense" every year pretty quickly. We then move into identifying functions in tables, equations, sets of ordered pairs and graphs. We complete this free function or not sorting activity to get warmed up before moving on to more in-depth practice.
I really like matching activities because, like sorting activities, they can be given early in a unit and students can still work confidently on their own. The cards above are from a graphs to stories activity where students match function graphs to story problems. I was a HUGE Dexter fan (before the last season -- ok, before the last 3 episodes of the last season. I mean, really??), so all of the names in this activity are names of characters in the show.
This pink card is from one of my favorite activities we do each year. It's a set of evaluating functions task cards. There are so many questions! Students are asked to evaluate functions given tables, graphs, equations and word problems and the activity usually takes us multiple days to complete. I like to count it as a quiz grade because of how much work my students have to do to complete it.
I find that every year my group of students needs a little more practice in one area. Some years they need more practice evaluating, other years they need more help identifying, etc. This super-discounted bundle has a huge variety of functions activities that give students practice with functions without being boring. Each individual activity is also hyperlinked on the page if you need something specific.