Saw this interesting problem posted on twitter today by Michael Pershan:

As I mention at the beginning of the first video, we are not studying this type of problem right now, but I thought it would be interesting to see my son try to work through it. His solution isn’t fast or necessarily a direct straight line to the answer, but it was indeed interesting. This is what learning math looks like.

In the first part I introduce the problem and my son begins to work toward the solution. His instincts are to find the length of the square. He manages to find that length at the end of this video:

After finding the side length of the square, my son is pretty puzzled as to what to do next. He spends a lot of time looking at the picture and even draws in an extra triangle. Eventually he wonders a little bit about symmetry and draws in a few other triangles. Without knowing it, yet, he’s inches away from solving the problem.

At the end of the last video my son thought that finding what A + B in his picture was, that would be a good step towards the solution. Funny enough, he’s got the answer written down on the board, but he doesn’t see the geometry right away and begins to doubt that he’s on the right path. Interesting he changes the approach to trying to find the area of the triangles and then the area of the square – this thought will help him out tremendously just a few minutes later.

Suddenly – at 2:16 in the video – he sees the connection and the whole solution to the problem falls into place.

Finally, we finish up the problem. I had him work through the quadratic formula off camera. Once he has those solutions, he’s able to write down the coordinates of the other corners of the square right away.

We wrap up this project by talking about a few other symmetries in the problem that could have allowed us to see the solution in a slightly different way.

Overall a fun little project. Sorry for the quick write up – only had 30 minutes to put the blog post together before having to run out the door.

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This is one of those nice problems for which an excess of knowledge is a real obstacle in the way of the two line solution. More like this, please !