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UKMT Intermediate Mathematical Challenge, 2017

Geometry Difficulty 2.0 Junior Find the answer United Kingdom

The diagram shows four equilateral triangles with sides of lengths $1, 2, 3$ and $4$ . The area of the shaded region is equal to $n$ times the area of the unshaded triangle of side-length $1$ . What is the value of $n$ ?

(A) $8$ (B) $11$ (C) $18$ (D) $23$ (E) $26$

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