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UKMT Grey Kangaroo, 2016

Geometry Difficulty 2.0 Junior Find the answer United Kingdom

Three equilateral triangles are cut from the corners of a large equilateral triangle to form an irregular hexagon, as shown in the diagram. The perimeter of the large equilateral triangle is $60$ cm. The perimeter of the irregular hexagon is $40$ cm. What is the sum of the perimeters of the triangles that were cut from the large triangle?

(A) $60$ cm (B) $66$ cm (C) $72$ cm (D) $75$ cm (E) $81$ cm

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