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[求助]一道PREP上的题,不知答案为何选它~~

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楼主
发表于 2009-10-18 17:03:00 | 只看该作者

[求助]一道PREP上的题,不知答案为何选它~~

A circular jogging track forms the edge of a circular lack that has a diameter of 2 miles. Johanna walked once around the track at the average rate of 3 miles per hour. If t represents the number of hours it took Johanna to walk completely around the lake, which of the folowing is a correct statement?

正确答案:2.0<t<2.5

我的解题思路:2pai*1=3t,

但解出来不对啊~~我不知错哪了,恳请高人帮帮忙~~万分感谢!!!!!

沙发
发表于 2009-10-18 17:20:00 | 只看该作者
楼主解得没错,t=2pi/3,这个数就是2.0<t<2.5的
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