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A decorative grille is built from a motif repeated around a centre. Designer Anya wants the smallest angle of rotation to be a whole number of degrees AND wants the order to be more than 8 but less than 12.
Which order gives a whole-number angle of rotation?

Class 7Rotational SymmetryGeometry
  • Aorder 9 (40°) and order 10 (36°)
  • Border 11 only
  • Corder 9 only
  • Dnone of these give whole numbers

Step-by-Step Solution

360/9 = 40 and 360/10 = 36 are whole numbers; 360/11 ≈ 32.7 is not. So orders 9 and 10 work.
Answer: A) order 9 (40°) and order 10 (36°)

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