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Geometry and TrigonometryEasy–MediumPaint needed for a box's outside

Geometry and Trigonometry practice question

A closed box is 7 cm by 4 cm by 3 cm. Which expression gives the total area, in square centimetres, to be painted if all six outside faces are painted?

  1. A. 2(7 × 4) + 2(7 × 3) + 2(4 × 3)Correct
  2. B. 7 × 4 × 3
  3. C. 7 × 4 + 7 × 3 + 4 × 3
  4. D. 2(7 + 4 + 3)

Answer: A. 2(7 × 4) + 2(7 × 3) + 2(4 × 3)

Surface area of a box: two of each of the three different faces.

Why the other answers are wrong

B. 7 × 4 × 3
7 × 4 × 3 is the volume.
C. 7 × 4 + 7 × 3 + 4 × 3
Counts each face once; a box has two of each.
D. 2(7 + 4 + 3)
2(7 + 4 + 3) adds edge lengths, not areas.

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