GRE考试

【单选题】The figure at the right consists of four semicircles in a large semicircle. If the small semicircles have radii of 1, 2, 3, and 4, what is the perimeter of the shaded region

A、10π
B、20π
C、40π
D、60πE、100π

网考网参考答案：B
网考网解析：
In the given figure, the diameters of the four small semicircles are 2, 4, 6, and 8, so the diameter of the large semicircle is 2 + 4 + 6 + 8 = 20, and its radius is 10. The perimeter of the shaded region is the sum of the circumferences of all five semicircles. Since the circumference of a semicircle is π times its radius, the perimeter is π+ 2π + 3π + 4π + 10π = 20π. document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>