When I first started reading Swallows and Amazons with my math brain on, aka considering a unit, I thought I would end up with a geometry unit. The book itself had other ideas...
In this post I overview my process for beginning a unit. I'm considering running a course to help you see the math in any book, if you are interested please comment or email me!
When I start reading a book I simply make note of any maths language or references. Reading on a kindle makes this easy, although I do love reading hardcopies and making note in my trusty notebook. I highlight ANY thing that sparks my imagination. In Swallows and Amazons I first started considering what shape things would be. For example when Roger tacks up the field to his mother I considered the shape between his arms and also the path he was tracing across the field. I highlighted "ran in wide zigzags, to and fro". My first thought was to have children act this out (for kinaesthetic learners) and then draw it (for visual learners) and discuss the shapes, the effect of the angle on the size of the triangle etc. So I jotted down this idea (which didn't make it into the unit).
I continue on through the book highlighting passages that may tie with the math syllabus or just spark my interest. For example "Supper at half-past seven, and not a minute later" could lead to and activity on time, "a fourteen-foot dinghy with a brown sail" may lend itself to a measurement activity (I have a similar activity, How Big is a Bear, in The Little House Unit). In Swallows and Amazons and Fractions I included links to non mathematical ideas that may be of use in a unit study, so I also highlighted subjects that I wanted to know more about such as "You can be Queen Elizabeth going aboard the ships at Greenwich". I researched this later and provided links to information in the unit.
About a third of the way through the text, I realised that my original focus of geometry was being out weighed by fraction references. Some of my original ideas I re framed to include fractions. For example I love the reference to Titty making a sail (fellow sewer here!) and had originally thought we could make sails out of a variety of shapes, considering at the nautical flags as examples. In the final unit, mathematicians instead find what fraction each colour in a nautical flag is.
After I have highlighted and made brief notes I consult the Australian Curriculum to get a feel for the level of mathematics to be aiming for. Obviously with your own children you will know where they are at and what is appropriate. I read the curriculum for the chosen area to see what sort of concepts are age appropriate and cover as many as I can, adapting my original ideas. This is usually where I draw out Advanced Pathway ideas as well.
With an idea of the mathematical skills and concepts, I then sit down and to figure out the best way to step through an activity. Writing an aim statement for the activity really helps at this point, to keep the focus in mind. This is the most time consuming stage for me as I want to write as clearly as possible to express my idea to some one who hasn't had the vision themselves, which is why photos become a vital tool for me to communicate with parents and teachers how the idea can look. I also challenge myself to include activities for a variety of learning styles. I may start off with a drawing activity and think, how could we take this outside or involve gross motor skills etc. For implementing in your own home it needn't take long at all, simply note what steps and questions you will need ask your child to encourage their exploration. Questions can be a great starting point to an activity, I wonder how far that was? Was John about half way round at the look out do you think?
Some of the activities are obviously linked to the text, such as John's Swim. In the text the children are yelling "You're nearly round" and instead we find what fraction of the distance John actually is.
Others come out of further research. For example Reefing the Sail and Sounding Lead both came out of my being inquisitive to find out more about these sailing terms. In my research I realised that there were fractions involved.
Once I've stepped out the activity, I write my lists - what you will need, key language etc. Then I create the Anecdotal Assessment sheets, linking back to that aim statement and the Australian Curriculum (just incase you need that for reporting).
I do feel blessed to be able to see mathematics in literature. I completely believe it is a way of seeing things that grows the more you exercise it, and I think that you can see it too! I've had parents email me, "oh I thought of this activity in this text", and I get so excited. Yes this is it! I think that after using my units you will start to see what I mean, and be able to take this skill and apply it to a lot of texts. Of course we don't always have time for that as busy parents and teachers... so don't worry I still plan on making more units :)