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Perimeter of triangles and quadrilaterals, step by step

A rectangle's perimeter can be found without really looking at the figure.

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The question
198198 cm

Perimeter of a 19 by 8 parallelogram

sides:198198
sides:198198
sides:198198
19 + 8 + 19 + 8=54 cm
  1. Perimeter is the distance round the OUTSIDE — the length of the fence, not the size of the field. That is the whole difference between this and area, and it is where the usual wrong answer comes from.
  2. So there is nothing to work out — just walk round the edge and add: 19 + 8 + 19 + 8.
  3. 19 + 8 + 19 + 8 = 54 cm. Note the unit: cm, not square cm — a fence is a length, and a length never gets squared.

How it works.

  1. 01

    Perimeter is the distance round the OUTSIDE — the length of the fence, not the size of the field. That is the whole difference between this and area, and it is where the usual wrong answer comes from.

  2. 02

    So there is nothing to work out — just walk round the edge and add: 19 + 8 + 19 + 8.

  3. 03

    19 + 8 + 19 + 8 = 54 cm. Note the unit: cm, not square cm — a fence is a length, and a length never gets squared.

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