GCSE Maths (AQA)

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Similarity & Perimeter

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Geometry and Measures Mensuration and Calculation

Similarity & Perimeter

4:40 Similarity Calculations
Spec R12 G19
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  • Perimeters of similar shapes have the same common ratio as their individual sides
  • Two shapes are similar if one is a larger or smaller version of the other
  • The perimeter of a larger shape is equal to the perimeter of the smaller shape multiplied by the scale factor
  • The scale factor is the ratio of the corresponding sides of the two shapes
  • The perimeter is found by adding the scaled sides together
  • The scale factor applies to all shapes, not just triangles
  • The scale factor can be calculated by comparing the lengths of corresponding sides
  • The perimeter of a shape is the total distance around the outside of the shape
  • The scale factor can be used to calculate the perimeter of a larger shape when given the perimeter of a smaller shape
  • The rule of using the scale factor to calculate the perimeter is a useful shortcut and can be applied to problems where only the perimeter is given.

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