Lets try and use this:
https://docs.google.com/a/cooper.oxon.sch.uk/spreadsheet/ccc?key=0Allu0kz0f5e6dEF3bVNtVm1XYXNYUmlabHY1VjBRMWc&authkey=CJa9zcMD
Choose a question to work on and try and work out how accurate you can be - you might like to annotate the spreadsheet with your reasoning...
