Problem 9 · 2021 Math Kangaroo
Medium
Spatial & Visual Reasoning
careful-counting
Edmund cut a ribbon as shown in the picture. How many pieces of the ribbon did he finish with?
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Answer: D — 12
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Hint 1 of 3
Follow the cut line and count every strand of ribbon it goes through.
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Hint 2 of 3
Each time the cut crosses the ribbon, it makes one more piece.
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Hint 3 of 3
So the number of pieces is one more than the number of crossings.
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Approach: count the crossings then add one
- Trace the straight cut and count the ribbon strands it slices through: there are 11.
- One whole ribbon cut in one place makes 2 pieces, so the pieces are always one more than the cuts.
- 11 + 1 = 12 pieces.
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