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UKMT Grey Kangaroo, 2017

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

Stan had 125 small cubes. He glued some of them together to form a large cube with nine tunnels, each perpendicular to two opposite faces and passing through the cube, as shown in the diagram. How many of the small cubes did he not use?

(A) $52$ (B) $45$ (C) $42$ (D) $39$ (E) $36$

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