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2016 Math Kangaroo

Problem 7

Problem 7 · 2016 Math Kangaroo Medium
Spatial & Visual Reasoning spatial-reasoning

Part of a rectangle is hidden behind a curtain (see picture). The hidden part is a

Figure for Math Kangaroo 2016 Problem 7
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Answer: A — triangle
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Hint 1 of 2
The whole shape is a rectangle; picture its straight edges where the curtain hides them.
Still stuck? Show hint 2 →
Hint 2 of 2
The slanted corner of the curtain cuts off only a small corner of the rectangle.
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Approach: reconstruct the hidden corner of the rectangle
  1. The curtain hangs over the rectangle and its lower edge slants across one corner.
  2. The piece left hidden between that slanted edge and the rectangle's corner has three sides.
  3. So the hidden part is a triangle.
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