In this activity students start with a blank document, building up an enlargement step by step. They can drag objects and/or the centre of enlargement around the screen or they can change the scale factor, immediately seeing the transformed image.
A TI-Nspire document can be used later, allowing students to explore the similarity of triangles on a unit grid and to investigate the areas and perimeters of similar pentagons.
This activity forms part of the OxBox, published by Oxford University Press to support their course 'Oxford GCSE Maths'. http://www.oup.com/oxed/secondary/2010gcse/