Enlargement

Teachers' Notes

The programme aims to enhance other teaching of this topic by offering scale factors and effects that would be difficult to replicate in the classroom. Powerful visual images support each of the concepts covered. The content assumes little prior knowledge, although some preparatory work on ratios in similar figures would be helpful prior to viewing. The following are addressed specifically:

• Enlargement by a given scale factor
  
• Calculating a scale factor using ratios of sides
  
• Reduction using a fractional scale factor (including a 3-dimensional object)
  
• Using a centre of enlargement to place an image on a grid
  
• Finding a centre of enlargement
  
• Changing the centre of enlargement

The programme could be used to introduce the topic of enlargement or to provide enrichment alongside classroom teaching. Some students may benefit from viewing short sections of the programme as they progress through stages of the work and then view the entire programme to summarise the main points. The programme would be useful as a revision tool and it could also be used to consolidate knowledge at the end of teaching the topic.

Students could consider how many of the real Jamie stocks would fit on the blown up version. The scale factor of the Harry Potter poster was 185. Students are asked to work out the width of the word 'Harry' on the poster, given that it is 4.9cm on the design.

The answers to Worksheet 1 could be used as the basis for a discussion after viewing. For revision purposes, students may find it useful to have their own copy of the Key Facts and Exam Tips section of these notes. These could be edited and amended to meet individual needs.