Problem 16 · 2012 Math Kangaroo
Medium
Spatial & Visual Reasoning
transformationsspatial-reasoning
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Answer: A
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Hint 1 of 2
When a coin rolls around an equal coin, it spins faster than you might expect.
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Hint 2 of 2
Rolling halfway around an equal-sized coin turns the rolling coin a full turn, so its picture comes back upright.
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Approach: rolling-coin (one full turn over a half-trip)
- A coin rolling around another coin of the same size makes one extra spin for every half-trip around it.
- Going to the position shown, the upper coin completes one whole rotation.
- So its picture ends up the same way up as it started, which is position A.
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