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MathNet 2023-part-06 — 191 problems (EN–VI) Question 38

Math Olympiad Vault · MathNet 2023-part-06 — 191 problems (EN–VI)

Question 38

On the cube $A B C D E F G H$, denote the centre of the face $E F G H$ by $P$ and the midpoint of the edge $A B$ by $R$. The plane $\Sigma$ containing the points $C, P$ and $R$ intersects the edges $E F$ and $G H$ at the points $X$ and $Y$, respectively.

a) Prove that $|E X|:|X F|=|G Y|:|Y H|=1: 3$.

b) The plane $\Sigma$ divides the cube into two parts.
Determine the ratio of the volumes of these two parts.