Here is a 5th grade mathematics question:

"How much is one dollar plus one Indian rupee?"

Even a 10 year old would probably tell you that the answer is not $2 (or Rs 2)!

But try this in Microsoft Excel (or Google Docs) - these cutting edge tools don't seem to know better than a ten year old!

Live Spreadsheets provides a unique capability that handles formulae containing cells with different currencies. When you have instances like this in your spreadsheet, Live Spreadsheets guides you to the right currency exchange rates or lets you apply your own rates with reference to the base currency (currently US dollar).