How many quadrilaterals are drawn in this figure?
Hint: Be sure to count both convex and concave quadrilaterals.
There are 18 convex quadrilaterals, all coming from the 2×3 block at the top. Each of these is in a 1-1 correspondence with the concave quadrilaterals by extending the sides downward to meet at the bottom. In total, there are 36 quadrilaterals.
- Problem by David Vreken
- Solution by Jeremy Galvagni
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