Problem 11 · 2021 Math Kangaroo
Medium
Spatial & Visual Reasoning
cube-viewscomplementary-counting
18 cubes are coloured white, grey or black and stacked into the block shown. The figures show the white part and the black part on their own. Which of the following is the grey part?
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Answer: E
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Hint 1 of 2
The whole block is white cubes plus black cubes plus grey cubes, with nothing missing.
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Hint 2 of 2
The grey part is just the leftover cubes — the exact shape that fills the holes the white and black pieces leave behind.
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Approach: the grey piece is the leftover after taking out the white and black
- Imagine lifting the white cubes and the black cubes out of the big block.
- Whatever cubes are still sitting there make up the grey part — it exactly fills the gaps the white and black left.
- Matching that leftover shape to the pictures gives option E.
- So the grey part is E.
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