Problem 5 · 2025 Math Kangaroo
Easy
Spatial & Visual Reasoning
path-tracing
Markus pulls on both ends of each rope at the same time. Which rope forms a knot?
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Answer: C
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Hint 1 of 2
Imagine pulling each rope tight - most will just straighten out.
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Hint 2 of 2
Only a rope whose ends pass through the loop the right way will tighten into a real knot.
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Approach: check which crossing pattern stays tangled when pulled tight
- When you pull a rope's ends, a fake tangle simply slides apart and straightens.
- A true knot keeps a loop locked even after pulling.
- Checking each picture, only option C stays knotted.
- So rope C forms a knot.
Mark:
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