Problem 9 · 2010 Math Kangaroo
Medium
Geometry & Measurement
perimeter
What is the perimeter of the figure shown (all angles are right angles)?
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Answer: E — 46
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Hint 1 of 2
Because every corner is a right angle, all the flat pieces together reach across the full width and all the upright pieces add up to the full height.
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Hint 2 of 2
The whole outline is just (width + width) plus (height + height).
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Approach: slide the steps to find total width and height
- Slide the three flat top pieces up to one line: \(5 + 5 + 5 = 15\), the full width.
- Slide the three upright drops to one side: \(2 + 4 + 2 = 8\), the full height.
- Going all the way around uses each twice: \(15 + 15 + 8 + 8 = 46\) — the answer is E.
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