Explain the idea of using a spreadsheet to work out a running balance. The opening balance is shown at the top, and the cost of each item you buy is subtracted from it. The closing balance is the money which you still have after everything has been bought.

Give out the printed sheet. Ask pupils to work out the cost of items bought. Given an initial £20 to spend, they have to keep a running balance.

After the first part of the sheet has been completed by hand, bring the class together again. Add up the total spent and subtract it from the opening balance to check that the closing balance is correct.

Ask children to think about the processes used and the formulae they would need to enter if setting it up as a spreadsheet. Record the formulae on the second part of the sheet. Expect the more capable pupils to spot a pattern in the formulae as they are written down.

A spreadsheet is part set up on the computers. All pupils need to do is to enter the formulae. Compare these with pencil calculations to see if the results agree.

Ask children to play around with quantities to see what happens to the final balance. How close can they get to zero without overspending? Cheating by altering the prices to achieve a zero closing balance is not allowed!

What will happen if prices are discounted by 10% in the sale?

Review examples produced by the class. Double the opening balance: what can we buy now?
Did some children see negative amounts? Why did this happen? Try an example and discuss the meaning of the closing balance.