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【OG20-P166-130题】
After driving to a riverfront parking lot, Bob plans to run south along the river, turn around, and return to the parking lot, running north along the same path.After running 3.25 miles south, he decides to run for only 50 minutes more. If Bob runs at a constant rate of 8 minutes per mile, how many miles farther south can he run and still be able to return to the parking lot in 50 minutes?
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8minutes行驶1mile,那么行驶了3.25mile对应用了3.25*8=26minutes,还可以继续开50minutes,所以总的时间为26+50=76minutes,那么单边的时间则为76/2=38minutes,对应为38/8=4.75miles,那么还能够继续向south行驶的距离为4.75-3.25=1.5miles
题目讨论 (6条评论)

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TOBEAWESOME
设继续往南走x,那么回程总共长3.25+x。注意!!是继续向南走+回程一共不超50min,所以是x+3.25+x=50/8。做的时候忘了把刚开始的x加上了。
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0 回复 2020-12-16 16:24:44
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1289311ww
眼瞎看成8公里每分鐘。。。。。
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0 回复 2019-12-26 21:08:27
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358379z
开始我理解错了,以为还要往南开50分钟 (50/8-3.25)/2=1.5
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0 回复 2019-09-09 08:20:27
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盐饮
根据题意,之后只想走50mins,包括走往南剩余的路和返回 8 mins per mile—1mile-1/8 mins 3.25+1/8*(x)=1/8*(50-x) X=12, 1/8*(12)=1.5
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0 回复 2018-10-01 09:21:39
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郑煜祺
剩下50分钟最多跑 50/8=6.25m 包括了2x和往回跑的3.25设再往南跑x3.25+2x=6.25x=1.5
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0 回复 2018-08-07 13:32:57
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MYYHH
这一题最关键的信息点是 a constant rate of 8 minutes per mile ,中文是八分钟每米 ,这个并不是速度,速度单位应该是路程除以时间,而不是时间除以路程, 所以速度是八分之一米每分钟。设还可以跑x mile,然后是(2x+3.25)/ 1/8= 50.求得x=1.5.
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0 回复 2017-12-08 13:23:01