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GCSE Maths students find writing about charts hard work. A discussion based activity came to mind where each group had to discuss a chart, write some sentences, then compare the sentences they wrote. As a further slightly devious twist, each group would have a different chart from the group next to them.

I used a spreadsheet to generate three different types of chart from the same (made up) data. The fabricated data has certain easily spotted proportional relationships, and tells a simple story of low trade on Mondays in Freda's tea stall.

## The charts

Charts were coloured using a greyscale palette so they can be printed in monochrome. The images below should copy and paste into most of the interactive whiteboard packages and into PowerPoint or Impress for class discussion after the group activity.

## The group activity

Each group of about 3 students had copies of a handout showing one of the three types of chart. The handout asked them to write a few sentences about what the chart told them, and to try to use keywords in their sentences. The group was asked to polish up one of their sentences to present to the rest of the group.

The percentage bar chart should be given to the group with students you want to 'stretch and challenge' in the OFSTED jargon - they don't know about the absolute numbers of drinks sold, and they will need to formulate sentences about changes in percentage.

I found that I had to do a lot of coaching to get students to compare proportions and to use fraction language, to estimate fractions and ratios between aspects of the data.

I had mini whiteboards out for the groups to write the 'polished' sentences on. The groups rotated their mini-whiteboards (usually about 6 or 7 groups) and commented on the other sentences. Groups then saw the charts the other groups had.

Some sentences were picked out and written up on the whiteboard.

## Outcomes

• The groups with the dual/clustered and stacked/composite bar charts all worked out that there was a large increase in sales between Monday and Tuesday, and that the proportion of coffees sold increased as well between Monday and Tuesday.
• Most of these groups worked from numbers of drinks read from the graphs. Only in one case did I have to explain how to estimate numbers from the stacked bar chart.
• The widest variation in sentences came from the groups who had the percentage bar charts. More coaching was needed to write sentences about the change in proportions of the drinks sold between the days.
• Many groups recognised the decrease in the number and proportion of cold cans sold on the Tuesday and recognised the contrast with the sales of warm drinks. Many wanted to explain this by saying it was colder on Tuesday
• Very few people used the information in the photograph about prices to estimate revenues - those that did had experience of retail!
• A lot of people wanted to do something about the larger proportion of coffee sold on Tuesday: two for one offers on other drinks to clear stock or loyalty cards or something.
• Students were able to articulate the differences in emphasis between the dual/clustered and stacked/composite charts easily (totals/differences) and the percentage bar chart with a bit more prompting

Students had chart interpretation questions from the AQA Practice Sets as homework, and generally did well. I think this 45 minute activity covered basic chart reading and gave students practice in writing sentences about maths in a way that allowed coaching for those new to graph work, and that allowed a degree of challenge for those familiar with it.

We also compared tea stalls, cafes and catering generally in the local area. I deliberately mixed up the groups so as to have people who had not worked together much in each group. Social factors can help making people more comfortable in Maths lessons.

Keith Burnett, Last update: Sun Dec 15 2013