Sharing Kelsey Houston-Edwards’s bridge video with kids

Kelsey Houston-Edwards published another fantastic video this week:

By coincidence my kids had been making domino runs this week and I was already planning on doing this bridge activity with the boys – perfect timing! Even better, Houston-Edwards’s video shows that this activity is a great way to introduce kids to basic mathematical modelling. That topic has been on my mind quite a bit this week too because of the new Grant Sanderson calculus series.

So, we watched the video on Friday night and talked about some of the ideas this morning.

Here’s a short introduction to the problem and a bit about what the boys remembered from the video:

Next we moved to the problem of trying to use some basic math to describe what’s going on with these bridges. Although they’d seen the math modelling in Houston-Edwards’s video previously, the modelling ideas were not the first ideas that came to their mind. Instead they were able to solve the first step in the bridge problem. Instead they were able to just see that solution.

With the algebraic solution not being quite the first thing that came to their mind, I decided to dive into that solution for the bridge with 3 bricks. The nice thing about the 3 brick bridge is that the numbers are still not that complicated.

Once we had some equations written down we talked about various different approaches to solving them. My younger son found a pretty clever way to solve these equations without too much algebraic effort.

Finally, I had the boys make some bridges on the table rather than the slightly cheating way that we did in the first video. We had a bit of debate off camera about whether or not their top bricks were fully off the table, but they were certainly very close 🙂

Definitely a fun project. I’m going to try to do more of these modelling tasks in the next month or so. Right now I’m not completely sure where to find good introductory modelling tasks for kids, but hopefully solving that challenge will be a fun project for me!


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