[WCYDWT] Speeding In Compton

This one is about a year old. It’s short and simple. As I recall, I used it for an opener problem and nothing more. In my development as a math teacher and curriculum developer, though, it has a lot of sentimental significance. In Leslie Knope’s Love Life, I wrote about my goal to draw inspiration closer to action through practice, practice, practice, and this is the result.

I was driving along, checking Maps on my iPhone for directions, and found it interesting how the blue tracking orb moves faster when you’re zoomed in close to the map and slower when you’re zoomed out. Reflexively, I turned it into a question: “how fast is the car going, given this particular orb?” Then I tweaked it: “Do we arrest this person for speeding?” (Crime doesn’t pay, but it’s more interesting to my students.) Then, just as reflexively, I knew the image I needed to create.

iPad – No Timer from Dan Meyer on Vimeo.

Such a simple thing, but it was one of the most satisfying moments of my professional life.

The Goods

The problem archive, including:

  1. the video with the timer,
  2. the video without the timer,
  3. a photo of a speed sign at that intersection in Compton,
I'm Dan and this is my blog. I'm a former high school math teacher and current head of teaching at Desmos. He / him. More here.


  1. This will have no particular bearing on this problem, but I want to thank you for your tremendous contribution to teaching math. I was an excellent math student – with one goal: to pass calculus so that I NEVER EVER EVER had to take math again. (On the other hand, I did use differential calculus this fall to figure out the slope of our front porch to keep water from pooling on it as we rebuilt it.)

    My husband, who is a very quick and bright man and who gets most math correct by instinct, freezes at the sight of a fraction and blanches upon seeing an algebraic equation. He was taught to fear the wolverine of math.

    I was taught to see it as a very large German Shepherd that would obey if treated right, and sink his teeth into your thigh if you got flip.

    My children are homeschooled. We use the MEP math curriculum, which is all about trying things and seeing what works. It’s about whiteboards and erasers and scales and and jellybeans and tiles on the kitchen floor and bricks on the front walk and math applied to reality. It’s our third math curriculum and the first that has helped them *understand* the math functions they are using, not just complete the formula.

    Our last math curriculum was doing a good job of drilling math facts, but at the end of the year, neither of my oldest two could understand WHY any of it worked or how to solve the same problem looked at from a different angle.

    Your blog inspired me, committed me, challenged me to find a math curriculum that encouraged them to grapple with math and find the puppy who wanted to play.

    As a result, my kids (5, 6, 8) play multiplication games in the car for fun. They can solve algebraic unknowns if the numbers involved are 5 or less (so far: we are only 1/4 of the way through our school year). They shout and dance and run to sharpen pencils and get their erasers ready.

    These posts about Google Maps and hoses and escalators – they aren’t applicable to my kids just yet, but they inspire me to go find interesting, applicable math challenges for the level we are on.

    Really, thank you. You even have my husband intrigued with math again – he may have wolverine flashbacks, but he’s stopped running out of the room when it appears.

    Blessings to you and keep up the good work. It really is so very important.
    Pip Chambers

  2. Dan,

    I love the work you do on my behalf and on behalf of my students. We are having fun with the videos. I am a disciple of what you are trying to do. I am also trying to spread the word about making math creative and divergent “again”. Keep up the cool work.

  3. Dan,

    Another great post. Thank you for inspiring teachers like Pip to teach math in a meaningful way, connected to real life experience.

    This is *exactly* what I teach my preservice teacher students. It is so refreshing to find another teacher blogger who cares about the understanding of math by students, not just the doing of it.


  4. I like this problem. A lot. But I’m curious as to where you draw the line with complete fabrication. I played with the idea of manipulating the times in my toaster problem to get a linear regression out of the first four settings. In fact, I made it just to see if I could, but never out it in front of my kids.

  5. Dan,

    Stumbled across your blog recently – very interesting. Your use of the video camera is genius! Below is my first attempt at doing something similar. Took the better part of a weekend but a lot of that was picking a video editing program & learning how to use it. You seem to have a lot of motivated and interesting followers – it would be nice if we had more of this kind of thing to share amongst ourselves and spark new ideas.


  6. I’m a little embarrassed to even mention this, but my students got about 140 mph, and I couldn’t find their mistake. You’re going about 4000 feet in 20 seconds, right? That’s well over 2 miles per minute, and therefore over 120 miles per hour. My car can’t even go that fast, and I sure as heck wouldn’t try it on a residential street and through an intersection. Can someone help me out here? Is this a real trace, and we’ve made a mistake, or what?


  7. Holy cow. That never crossed my mind. I think this will be a big relief to my students as well as myself. They’ve been well engaged with a number of the WCYDWT problems, but this one left all of us a little perplexed. Even with the problems (e.g. The Daily Show ones) that don’t have anything like a precise answer, they’ve been able to understand what’s going on and explain it in one way or another.

    Knowing the answer now, I imagine I would approach the end stage of the process differently, with questions designed to help them “climb out of the box” and look to the sky.

    Thanks, Dan!

  8. That’s a ways north of Compton, in a neighborhood called Hyde Park. (the southern tip of Crenshaw) I did this with my students and loved that they made the observation that the light at Slauson and Crenshaw is the longest light EVER. Made me think that this Google Maps approach would also be great for physics teachers attempting to explain instantaneous velocity, average velocity, acceleration, etc.