Talking about proportions in my Pre-Pre-Algebra class (called Integrated Math). We got on the topic of exchange rates. A student asked how you can make money through exchange rates. I’m a big fan of these Google graphs. Lots of questions to ask. We assumed we invested $1000 in Euros and exchanged them again to see if we made profits. Lots of questions you can explore here…. also a very scalable problem for higher classes.