大圆半径是小圆半径的3倍，大圆周长是小圆周长的（ ）倍，大圆面积是小圆面积的（ ）倍．
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设小圆的半径为r，则大圆的半径为3r，
大圆的周长：3.14×2×3r=18.84r，
小圆的周长：3.14×2r=6.28r，
则18.84r÷6.28r=3倍；
大圆的面积：3.14×（3r）2=28.26r2，
小圆的面积：3.14r2，
则28.26r2÷3.14r2=9倍；
答：大圆周长是小圆周长的3倍，大圆面积是小圆面积的9倍．
故选：C．
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| Some years ago, Chinese high school students would show their school-bags, new clothes or new pens to their classmates when the new term started, Today, however, all have 1 . If you still come back to school 2 only these things, you are falling out-of-date (过时). Students in big cities like to bring the latest high-tech things to school, and feel happy and 3 to show off (炫耀) these things to 4 . Mobile phones, MP3 players, CD players, electronic dictionaries, the list is endless. Young people think that, living in the twenty-first century, they must keep up with the 5 . They don't want to fall 6 . Besides, they think 7 they need to keep in touch with their classmates, so they need mobile phones. They also like to 8 the pop music, so they need CD players. They explain that, 9 like electronic dictionaries, these can be 10 in their study, 11 . They think that their parents should understand 12 they want these things. Foreign students will also bring some latest high-tech things when they 13 to school at the beginning of a new term. 14 , they often use the money which they made by themselves during the holiday to 15 these high-tech things that they want. | ||||
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