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Year 8 · Measurement

Surface area of rectangular prisms

Surface area is the total area of all six faces of a box.

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How to do it

  1. Find the area of the three different faces.
  2. Each appears twice, so double each and add.

Worked example

A box is 8 cm long, 9 cm wide and 3 cm high. What is its surface area, in cm²?
Six faces in three matching pairs: 2 × (8×9 + 8×3 + 9×3) = 2 × (72 + 24 + 27) = 246.
Answer: 246

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Six faces, in three matching pairs.

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