The diagram shows an equilateral triangle divided by three straight lines into seven regions. The three grey regions are equilateral triangles with sides of length 5 cm and the central black region is an equilateral triangle with sides of length 2 cm.
What is the side length of the original large triangle?
Select one option, then click Submit.
18 \text{ cm}
19 \text{ cm}
20 \text{ cm}
21 \text{ cm}
22 \text{ cm}
Select an option, then submit.
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Intermediate Mathematical Challenge 2012 (2012)
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