题目
Consider two circles A and B for which the following is true: the diameter of circle A is 8 times the radius of circle B in centimeters.
In the table below, select the values for the areas of circle A and circle B that are consistent with the information above. Make only two selections, one in each column.
解析
考虑两个圆A和B,以下情况成立:圆A的直径是以厘米为单位的圆B半径的8倍。
设圆\(B\)的半径为\(r\)厘米,那么圆\(A\)的直径就是\(8r\)厘米,所以圆\(A\)的半径为\(4r\)厘米。
根据圆的面积公式\(S=\pi R^{2}\)(\(S\)表示面积,\(R\)表示半径)
圆\(A\)的面积\(S_{A}=\pi(4r)^{2}=16\pi r^{2}\)
圆\(B\)的面积\(S_{B}=\pi r^{2}\)
所以圆\(A\)的面积是圆\(B\)面积的\(16\)倍。
逐一分析选项,只有当圆\(A\)的面积为\(64\pi\)(即\(r = 2\)时,\(16\pi r^{2}=16\pi\times2^{2}=64\pi\)),圆\(B\)的面积为\(4\pi\)(\(\pi r^{2}=\pi\times2^{2}=4\pi\))时满足圆\(A\)的面积是圆\(B\)面积的\(16\)倍这一关系。
综上,圆\(A\)的面积选\(E\),圆\(B\)的面积选\(A\)。