Problem 10 · 2009 Math Kangaroo
Medium
Spatial & Visual Reasoning
path-tracing
Which of the following tangles is made using more than one piece of string?
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Answer: B — I, III and V
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Hint 1 of 2
Trace each tangle: follow one strand and see whether it covers the whole figure before returning.
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Hint 2 of 2
If a single loop covers everything it's one piece; needing a second loop means more than one.
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Approach: trace each strand to count separate loops
- For each diagram, follow the cord from a start point and see how many separate closed strands the tangle really contains.
- Tracing the crossings shows that diagrams I, III and V each require more than one piece of string, while the others can be made from a single loop.
- So the ones using more than one piece are I, III and V.
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