16.用4根同样长的绳子围成下面4个图形,面积最大的是( )
| A. | B. | C. | D. |
15.一个圆环,外圆直径10cm,内圆直径8cm,求这个圆环的面积,正确的列式是( )
| A. | (3.14×102-3.14×82)÷2 | B. | 3.14×(10÷2)2-3.14×(8÷2)2 | ||
| C. | 3.14×(102-82)÷2 | D. | 3.14×(10÷2-8÷2)2 |
14.甲乙两圆的半径比是5:8,它们的面积比是( )
| A. | 5:8 | B. | 8:5 | C. | 5π:8π | D. | 25:64 |
12.在一张长8cm,宽6cm的长方形纸内剪一个最大的圆,圆的周长是( )
0 126933 126941 126947 126951 126957 126959 126963 126969 126971 126977 126983 126987 126989 126993 126999 127001 127007 127011 127013 127017 127019 127023 127025 127027 127028 127029 127031 127032 127033 127035 127037 127041 127043 127047 127049 127053 127059 127061 127067 127071 127073 127077 127083 127089 127091 127097 127101 127103 127109 127113 127119 127127 199269
| A. | 25.12cm | B. | 18.84cm | C. | 12.56cm | D. | 9.42cm |