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2022 Math Kangaroo

Problem 12

Problem 12 · 2022 Math Kangaroo Medium
Spatial & Visual Reasoning path-tracing

There are 5 trees and 3 paths in a park, shown on the map. One more tree is planted so that every path has an equal number of trees on each side of it. In which section of the park is the new tree planted?

Figure for Math Kangaroo 2022 Problem 12
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Answer: B — B
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Hint 1 of 2
Each path must split the trees so equal numbers sit on each side; count trees per side of every path now.
Still stuck? Show hint 2 →
Hint 2 of 2
The new tree must fix every path's balance at once; find the single section on the correct side of all three paths.
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Approach: balance every path at once
  1. Right now each of the three paths has an unequal split of the five trees.
  2. Adding one tree must even out all three paths simultaneously.
  3. The only section that sits on the short side of every unbalanced path is B, so the answer is B.
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