Problem 23 · 2011 Math Kangaroo
Stretch
Spatial & Visual Reasoning
tiling-tessellation
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Answer: D — Shape D.
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Hint 1 of 2
Adding the right shape should leave no room for any of the other four.
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Hint 2 of 2
Test each candidate: place it, then check the four leftover shapes can't fit anywhere.
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Approach: check which addition blocks all the others
- Two shapes are already on the 5×5 board, leaving some empty cells.
- Try adding each of the five shapes and see whether the remaining gaps still admit any of the other four.
- Only shape D, once placed, leaves gaps too small or wrong-shaped for any of the other four.
- So Lina should add shape D.
Mark:
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