问题
单项选择题
圆柱底面积为S，侧面展开图形为正方形，则这个圆柱的全面积是（）。
A.4πS
B.（1+4π）S
C.（2+4π）S
D.（3+4π）S
答案
参考答案：C
解析：
设圆柱底面圆半径为r，则圆柱底面积为
，底面圆周长l=2πr，又侧面展开图形为正方形，则圆柱侧面积为
，则圆柱总面积为2S+4πS=（2+4π）S。
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圆柱底面积为S，侧面展开图形为正方形，则这个圆柱的全面积是（）。
A.4πS
B.（1+4π）S
C.（2+4π）S
D.（3+4π）S
参考答案：C
解析：
设圆柱底面圆半径为r，则圆柱底面积为，底面圆周长l=2πr，又侧面展开图形为正方形，则圆柱侧面积为，则圆柱总面积为2S+4πS=（2+4π）S。
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| I moved to a new neighborhood two months ago. In the house with a large 1 across the road lived a taxi driver, a single parent with two school-age children. At the end of the day, he would 2 his taxi on the road. I 3 why he did not park it in the garage. Then, one day I learnt that he had another car in his garage. In the afternoon he would come home 4 work, leave his taxi and go out for his 5 affairs in his other car, not in his taxi. I felt it was 6 . I was curious to see his personal car but did not make it until I 7 to be outside one evening two weeks 8 , when the garage door was 9 and he drove out in his "own" car: a Rolls-Royce (劳斯莱斯)! It shook me completely 10 I realized what that meant. You see, he was a taxi driver. But 11 inside, he saw himself as something else: a Rolls-Royce owner and a(n) 12 . He drove others in his taxi but himself and his children in his Rolls-Royce. The world looked at his taxi and 13 him a taxi driver. But for him, a taxi was just something he drove for a living. Rolls-Royce was something he drove for a(n) 14 . We go to bed every night and 15 every morning as parents or children, not as bankers, CEOs or professors. We go for a 16 as close friends or go for a vacation as a 17 . We love life as it is. Yet often, we base our entire happiness and success on how high we 18 the social ladder (阶梯)-how much bigger and better a 19 we have. And we ignore(忽视)our Rolls-Royce, by keeping it dusty in our garage. We should focus more on 20 we are than what we do! | ||||
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