Investigator Training

The Description:

The goal here was to use Dan Meyer’s “Bone Collector” 3Act problem, as the motivation for a series of lessons on scaling.


The basic premise is as follows:  I show the Bone Collector clip first (see the link above for the clip), tell them we need to figure out the shoe size of the killer because we need to make sure that the killer is not in the room.   Then I concede that I realize they are not trained investigators.  Thus I tell them that over the next couple days we will be doing some investigator training, to get them ready to take on this case.   I help a lot during the first two cases, but I provide little help during the Bone Collector case – and the good news is that they didn’t need much help on it after the investigator training.

CASE 1 “The Drug House”

For their first case, I used a google maps images (see Keynote or PowerPoint file below) of a huge house that I was calling a “known drug” house (It’s actually Michael Jordan’s house).  The goal is for them to calculate the area of the very suspicious large building at the bottom right of the picture, where a lot of cars are located.  I tell them the FBI wants to perform a raid but they do not know how many agents to send, because they don’t know the size of the building.  And they are waiting for our calculations to proceed.


I handout the above picture to each student.  Then do a little strategy session where they write down how they are going to calculate the size of the building.  At that point they are given time to solve it with their pair/share partner.

The next day  I come and say that althought the FBI was happy that we correctly calculated the size of the building, unfortunately after performing the raid they learned that this was not a drug house, it was in fact Michael Jordan’s house.  And that big building is a basketball court.

CASE 2 “The Statue Thief”

I use a picture of the Surfer Memorial Statue in Santa Cruz.  Then I show a the same picture but with the statue photoshopped out.  I then tell them that a security camera picked up a very suspecious person who had visited the statue multiple times before night of the theft , and that the FBI needs us to find the height of the suspect in the picture.  This case is very similar to the Bone Collector.


(awesome statue)


(sadly it was stolen)


(but we have a suspect)

Students get a copy of the image above.  We again do a strategy session, where I require them to write a strategy for finding the suspects height.

The next day I reveal that the suspect was captured and he is 6ft.  Most students calculate something around 6″3′, so we spend some time talking about possible sources of error.

CASE #3 The Bootprint

Here we do the actual Bone Collector problem, delievered in much the same way that is described in Dan’s blog.

The Advice:

– I have students work in groups of two.

– I don’t spend the entire class period on these.  I do investigator training for the first 20 minutes or so, and then move on to something else.  Thus I essentially make this investigator training week.

– I help the students with the strategy sessions for the two practice cases, and then leave it up to them for the Bone Collector problem.

– Definitely play up the investigation aspect of these cases.  I tell them how much investigator make and that they should take these cases to the polic department and interview for a job.  If a couple students complain the quality of the bootprint picture is not very good, respond with “Yeah, I’m not sure why the FBI would provide such a low quality image”.

– That is me in the picture for the “Statue Thief” problem.  That is definitely an added bonus if you can do it.  It allows me to completley deny it’s me, while also saying “Look it’s not enough to just tell the police the suspect is extremely good looking, we have to get them information about his height”.

The Results:

High level of engagement.  Take a listen to student reaction when they hear that the shoe print is a size 10.

Bone Collecter student reaction

The students were upset (yes, actually upset) because all their solutions were between size 13.5 and size 16.5 .  They all calculated a larger size because they used the bootprint, rather than the actual size of the foot inside the boot to convert to shoe size.   I ended the lesson with a great back and forth with the students about what happened with their calculations.

One of my lowest performing students asked me if her proportion she setup was correct…  it was.

Using the Bone Collector clip without the associated investigator training works too, but not as well for me.  I really enjoyed these lessons, and I felt like my two initial cases put the students in a place to be successful with the Bone Collector problem.

The Goods:

Dan Meyer – Bone Collector problem

The Drug House Handout

The Statue Thief Handout

Bone Collector Bootprint  (just pick one – my girlfriend and I messed around with the image in photoshop to get the best quality for different printers)

InvestigatorTraining   (Keynote and PowerPoint)  I created this in Keynote, and highly recommend using Keynote.

Update 1:

To see whether or not the students retained any of this, I put the following picture into the chapter test.  The question was:  How tall is the tree?


The guy in the picture was brave enough to take me on as his student teacher and I am a profoundly better teacher because of it.  His name is Walt Hays.  His height is 6ft.

Update 2: 3/23

Based on Debbie’s comment, I have fixed the typos in the Keynote and Powerpoint files and adjusted the scaling to result in an answer that is consistent with the size of the tennis court next to the basketball court building.



15 responses to “Investigator Training

  1. This is awesome. Like a candy shop.

  2. Thanks Dan! And great find with that Bone Collector clip – you kind of have me looking to capture math problems everywhere now.

  3. Speaking of surfing, my understanding is that they measure the heights of big waves by comparing them to a surfer’s thigh bone or some other fixed measure. PS. Did we ever run into each other when I lived in Santa Cruz?

  4. Pingback: dy/dan » Blog Archive » Great Classroom Action

  5. @Dan – I’ve lived in SC, but we never ran into each other. We did meet at your Mountain View Perplexity Session, but it was a big room. Now I’m living in the Peninsula, so it’s safe to say I try to make the trip to SC as much as possible. I have never been sure how they measure waves – I think I’ll look into it – probably find a great lesson in there somewhere.

  6. Is shoe length proportional to shoe size? I think if you graph length vs “shoe size” you get a y-intercept that’s not 0. Could that have been the source of their error?

  7. @Kevin – foot length is proportional to shoe size, but I agree not necessarily shoe length. Students need to make the observation that they are measuring the shoe length, and then estimate what is the most likely foot length. Then they must ask for the conversion between foot length and shoe size.

  8. Cool–thanks for sharing this! Will save this for proportions in Geometry! In the spirit of sharing and relevance to the shoe size discussion above here’s a similar project (google document link below) I’ve used with students on proportions in photographs. The sheet has the linear equation for converting length of foot to shoe size as well.

  9. The PPT has the dimensions on the basketball court building read in mm and then cm. Is this a typo, or am I missing something? Also, the tennis court next to the building is a great dimension reference. If it is a standard court, it should measure 78ft x 36ft. This means the building would be about 97.5ft x 48.75ft. Thanks for putting this together. My 6th graders are working on proportional ratios and they will love this. It will lead to them creating their own CSI mysteries for each other to solve.

    • Debbie – yeah that’s a typo, should be all cm. Last year I did this activity using feet and inches, but last summer I worked at Lockheed and the engineers there encouraged me to use metric measurements, so I made a last moment switch to metric and made some typos.

      Love the extentsion activity of having them create their own CSI mysteries, would love to hear how that goes.

      The numbers in the slide could be adjusted to get an answer of approximately 97.5ft x 47.75ft. When I had it in feet it did, but I did not adjust the scaling when I decided to move it to metric.

  10. Thanks so much for sharing this great activity! So highly engaging; I will use it this week!

  11. @Sarah – No prob. I hope your class gets a lot out of it. Would love to hear how it goes.

  12. Pingback: Math, Art Education, and Risk-Taking | 17GoldenFish

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