Shape and Space 9
2 marks · NormalThe diagram below shows a cuboid ABCDEFGH with AB = 4 cm, BC = 5 cm, and BF = 12 cm.
Work out the length of the space diagonal AE.
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13 cm (±0.05)
Also accept: 13.0 cm
Common mistakes: Using only two dimensions instead of all three.
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Marking points
M1 · 1 mark · Uses 3D Pythagoras’ Theorem:
A1 · 1 mark · Correct answer: cm to 3 significant figures or as exact value. (follow-through)
Worked solution
In a cuboid, the space diagonal can be found using 3D Pythagoras’ theorem: