Spreadsheets are useful for investigating what happens when the data in tables changes. This is called creating a mathematical model or simulation and spreadsheets are helpful here because:
• the effects of changing numbers can be seen straight away as the formulas using them re-calculate new answers automatically;
• graphs can be drawn quickly and neatly to show any patterns or relationships in the data.
Working out a Party Budget

A class of thirty children want to organise a Christmas party. Everybody wants to eat at least five items of food but they only have £30 to spend.

The class carried out a survey to find out what each child wanted to eat and created a spreadsheet to simulate what would happen if they bought all these items in a shop.

Unfortunately the spreadsheet suggested that the party was going to be too expensive. When they drew a pie chart to show how many of each item was to be bought however they realised that the least popular item was the most expensive one.

What would happen to the total money spent if no jelly tubs were bought? They therefore adjusted the quantities in their spreadsheet to test their prediction that not buying any jelly tubs would give them move money to spend on more popular items and so keep their party within budget.
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