Real Functional Maths

I like maths. I like maths because it's useful, but sometimes in class that is not always obvious. Imagine my delight when I got this email from my little brother (OK, he's 26, but compared to me..).

So we're having a little trouble working out a backup plan should the ash cloud ground our flights next month... we plan on booking a backup coach/train combo to get to barcelona in case Vatnajokull kicks off again.

The plane fare is refundable if the ash kicks off - its price is £75.

For the coach/train, we have two options. One is half refundable - total price £100, but £40 of that is refundable. The other is fully refundable - total price £159.50, all of that refundable.

We're putting the odds of Iceland ruining things at 50/50, so which one train fare is best - half or full - to get based on the prices involved?

This got me thinking. Partly thinking about how to solve the problem, and partly "ooh - that's a good lesson idea".

Anyhow, here is the spreadsheet I wrote ...

The full link is here...

Now all I need to do is turn it into a lesson. Modelling, excel skills, researching prices, ...