In this lesson you practise the Excel formulas everyone needs at work: cell references, SUM, AVERAGE, IF and absolute references. Every step has a working spreadsheet in it, so you learn each formula by typing it and watching what it does.

Watch the sheet below: one formula prices a whole office supplies order.

In this lesson you'll:

• write formulas that use cell references, so totals update by themselves
• summarise a column with SUM, AVERAGE, MIN, MAX and COUNT
• copy a formula down a column, and lock the one cell it must always use
• make a decision in a cell with IF, and fix the errors you'll meet

It takes about 60 minutes. Click any cell above to see what it holds.