AMC 8 2007 Problem 23
AMC8 2007 年第 23 题
面积与周长（综合）★★★☆☆
What is the area of the shaded pinwheel shown in the grid?
下面 5×5 的网格中，阴影部分的面积是多少？
- A.4
- B.6
- C.8
- D.10
- E.12
正确答案 · Correct Answer
B
解析 · Solution
Solution 1
The area of the square around the pinwheel is 25. The area of the pinwheel is equal to Each of the four triangles have a base of 3 units and a height of 2.5 units, and so their combined area is 15 units squared. Then the unshaded space consists of the four triangles with total area of 15, and there are four white corner squares. Therefore the area of the pinwheel is 25-(15+4) which is
The pinwheel is composed of 8 congruent obtuse triangles whose base measures length 1 and height measures length 1.5. Using the area formula for triangles, the pinwheel has an area of
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