单选题A circle has an area of A, A second circle has a diameter four times that of the first circle. What is the area of the second circle?A2AB4AC8AD16AE32A
单选题
A circle has an area of A, A second circle has a diameter four times that of the first circle. What is the area of the second circle?
A
2A
B
4A
C
8A
D
16A
E
32A
参考解析
解析：
设圆1的半径为r，所以A=πr2，所以圆2的半径为2r，面积=2*π*(2r)2=16πr2=16A，故本题应选D项。
设圆1的半径为r，所以A=πr2，所以圆2的半径为2r，面积=2*π*(2r)2=16πr2=16A，故本题应选D项。
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