In the square, the midpoints of the two sides were marked and the segments shown in the figure on the left were drawn. Which of the shaded quadrilaterals has the largest area?
[img]https://cdn.artofproblemsolving.com/attachments/d/f/2be7bcda3fa04943687de9e043bd8baf40c98c.png[/img]
Problem 1241
Official solution
1. Identify the midpoints and draw the segments:
- Let the square be with side length .
- Mark the midpoints and of sides and respectively.
- Draw segments , , , and .
2. Analyze the quadrilaterals formed:
- The segments divide the square into four quadrilaterals.
- The quadrilateral with more dense cross-hatching is formed by the segments and .
- The quadrilateral with less dense cross-hatching is formed by the segments and .
- The middle quadrilateral is formed by the intersection of all four segments.
3. Calculate the areas of the quadrilaterals:
- The area of the entire square is .
- Each of the four quadrilaterals is a right triangle with legs of length .
- The area of each right triangle is .
4. Combine the areas:
- The middle quadrilateral is formed by the intersection of the four right triangles.
- The area of the middle quadrilateral is (since it is half of the area of the square minus the areas of the four right triangles).
5. Compare the areas:
- The quadrilateral with more dense cross-hatching is formed by combining two right triangles.
- The area of this quadrilateral is .
- The quadrilateral with less dense cross-hatching is also formed by combining two right triangles.
- The area of this quadrilateral is also .
6. Conclusion:
- Since the middle quadrilateral has an area of and the quadrilateral with more dense cross-hatching has an area of , the quadrilateral with more dense cross-hatching has the largest area.
The final answer is the quadrilateral with more dense cross-hatching.