Shape and Space 9
2 marks · EasyIn a square-based pyramid, each base edge is 6 cm and the vertex is 8 cm vertically above the centre of the base. Calculate, to 3 significant figures, the length of the slope from a corner of the base to the vertex.
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10.0 cm (±0.1)
Common mistakes: Use base edge instead of distance from centre to corner; Only use the height and not the 2D triangle
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Marking points
M1 · 1 mark · Correct method to find distance from centre to corner of the base ( cm or equivalent)
A1 · 1 mark · Full correct answer for slant edge ( cm, 3 s.f.)
Worked solution
The centre to corner of the square base is:
Now use Pythagoras' theorem on the triangle with base and height 8:
But this answer is incorrect for 6 cm base edge, height 8 cm. Each half-diagonal = . Correction (full-diagonal = , half-diagonal = , slant edge = cm.) Rounding to 3 significant figures: 9.06 cm.
So, the answer is cm ≈ cm (to 3 s.f.).