UKMT Pink Kangaroo, 2026

Combinatorics Difficulty 2.0 Junior Find the answer United Kingdom

Six woodworms made their home in an old wooden cube made up of identical small cubes. Each one drilled a tunnel all the way through the cube, parallel to one of its edges. The diagram shows the entrances to the six tunnels. How many small cubes do not have a tunnel drilled through them?

(A) $9$ (B) $12$ (C) $15$ (D) $18$ (E) $21$

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