One of the key practical things that unites European countries and increasingly unites the world is the metric system of measurement. It seems obvious to base measurement scales on base 10, with units divided into 10ths, 100ths, 1,000ths I but such a system is relatively recent in history. In Britain there has been considerable resistance to the metric system and "metrification", with people prepared to fight in the courts for the right to use the old imperial system of units. Even the Mathematics National Curriculum still requires pupils to know conversions between metric and imperial units.
* Discuss: Why does it make sense to have a common system of units? What makes the metric system so much easier to work with than imperial units? (Leads to discussion of base 10). Should the Mathematics National Curriculum mention imperial units at all?
* Construct conversion tables and charts - a useful exercise to reinforce ideas about proportionality.
* Look into the meaning of prefixes such as giga, mega, kilo, centi, milli, micro, nano and pico when tackling standard form.