Maths Olympiad Prep

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Problem 250

Geometry Difficulty 1.4 Multiple choice CEMC Cayley · Canada · 2022

Two identical smaller cubes are stacked next to a larger cube.
Each of the two smaller cubes has a volume of 8. The combined height of
the smaller cubes equals the height of the larger cube. What is the
volume of the larger cube?

Pick one

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Official solution

Since 2×2×2=82 \times 2 \times 2 = 8, a cube with edge length 2 has volume 8. (We note also that
83=2\sqrt[3]{8} = 2.) Therefore, each of the cubes with volume 8 have a height of 2. This means that the larger cube has a height of 2+2=42+2 = 4, which means that its volume is 43=4×4×4=644^3 = 4 \times 4 \times 4 = 64.

Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.