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UKMT Junior Mathematical Challenge, 2016

Combinatorics Difficulty 3.0 AMC 10/12 Find the answer United Kingdom

Each of the nine small squares in this grid can be coloured completely black or completely white. What is the largest number of squares that can be coloured black so that the design created has rotational symmetry of order 2, but no lines of symmetry?

(A) $4$ (B) $5$ (C) $6$ (D) $7$ (E) $8$

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