Using ICT in mathematics case study 16 - 'Similar triangles and ratio'
Headline
An attempt to get children to understand the properties of similar triangles and how to use the unitary method to calculate missing side lengths.
Context
13 Year 11 GCSE C/D borderline children. Nine boys, four girls
Teaching and learning objectives
To be able to answer questions relating to similar triangles.
ICT resources and context
IWB and individual computers enabled children to investigate similar triangles and calculate missing lengths. An activity from a website (www.estarters.com) was used, as was dynamic geometry software. A spreadsheet had been used to analyse children’s mock exam results to highlight this as a problem area. Each individual computer had been pre-loaded with a booklet of problems by the teacher, using the dynamic geometry software.
Explanation of the lessons (including materials used)
The starter activity reminded children of previous work on similar shapes. A drawing of a truck enlarged showed children how angles remained the same after the enlargement. Parallel number lines were drawn to find the multiplier (scale factor) when increasing from 4 to 10 (see NS Y8 Multiplicative relationships). This strategy was then used to find the length of a missing side in a triangle. Children practised the skill in their electronic workbooks created by the dynamic geometry software, and used the unitary method to determine the ‘dilate’ fraction (an American term used the software to describe enlargement). The plenary involved revisiting a poorly answered question from the mock GCSE exam, which children now had more confidence and success in answering.
Evaluation of the impact of the ICT on the learning
The dynamic nature of the geometry allowed children to gain a greater understanding of relationships between the triangles and their sides, and see the results of enlargements. The ICT elements enabled strong connections between mathematical processes to be made, which enhanced the children’s learning.
Children themselves reported: ‘I felt involved in the lesson instead of just watching’, ‘I like to have a visual picture to help me to understand what is happening. I could see how the triangle changed when I tried different scale factors and this will help me to remember what to do’, ‘the starter activity with the parallel lines was simple to understand and I could see how to find the scale factor of enlargement using the unitary method. It made sense’, ‘if you can have a picture in your head it helps you to remember what is happening’, ‘you can explore on the computer. It is not like writing it down in your book. You can easily undo a step if it is not right’.
Opportunities for further developments
The level of skill which the children demonstrated with the dynamic software showed that there would be a lot of scope for continuing to teach shape and related work by using it.
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