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UKMT Senior Mathematical Challenge, 2020

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

Diane has five identical blue disks, two identical red disks and one yellow disk. She wants to place them on the grid opposite so that each cell contains exactly one disk. The two red disks are not to be placed in cells that share a common edge. How many different-looking completed grids can she produce?

(A) $96$ (B) $108$ (C) $144$ (D) $180$ (E) $216$

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