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Packing 1x1x4 bricks into a 6x6x6 box

Question

Is it possible to fit 5353 rectangular bricks, each 1×1×41\times1\times4, inside a 6×6×66\times6\times6 box?

Short answer

No. Split the box into 2727 blocks of size 2×2×22\times2\times2 and colour them black and white like a 3D chessboard: 1414 black blocks (112112 cells) and 1313 white (104104 cells). Any 1×1×41\times1\times4 brick runs through two blocks of each colour, covering 22 white cells, so at most 104/2=52104/2=52 bricks fit, even though 53×4=212<21653\times4=212<216.

Adapted from Zhou, A Practical Guide to Quantitative Finance Interviews, sec. 2.3 Thinking Out of the Box, 'Box packing', p.9; question and answer rewritten by SelfMadeQuant.com.

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