题库搜索>问题求解PS-12531
A driver completed the first 20 miles of a 40-mile trip at an average speed of 50 miles per hour. At what average speed must the driver complete the remaining 20 miles to achieve an average speed of 60 miles per hour for the entire 40-mile trip? (Assume that the driver did not make any stops during the 40-mile trip.)
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当前版本由 GMACNMSL 更新于2020-04-24 13:39:00 感谢由 GMACNMSL 对此题目的解答所做出的贡献。总用时为2/3个小时，为40分钟，前一半路程用2/5个小时为24分钟，所以后半路程用时为16分钟，为4/15个小时，所以20、（4/15）=75
D
I am not sure if I did this the easiest way, but here's how I went about it.
40 miles/60 mph = average trip time
20 miles/50 mph = time it took to complete first 20 miles
20 miles/X mph = time it took to complete second 20 miles
therefore
40/60 hours = 20miles/50mph + 20miles/X mph.
Solved for X and you get 75
maxxxine
总路程 = 时间 x 速度 1st 20 mil = 2/5 x 50 2nd 20 mil = T2 x S2 Total 40 mil = 4/6 x 60 T2 = 4/6 - 2/5 = 4/15 S2 = 20/T = 20 / （4/15）= 75
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2021-08-29 20:19:53
言言子的自律粉
不要瞎胡算，按照平均速度等于总路程比总时间来算
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2020-09-20 11:46:42
VC FIGHT回复 言言子的自律粉
姐妹！同担 怎会如此哈哈哈哈哈哈
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2022-09-12 15:14:47
ericsheh
40/60=2/3h 2/3h-2/5h=4/15h 20miles/(4/15h)=75 mph
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2020-08-07 17:15:39
Lee720
路程 速度 时间 第一段 20m 50m/h 2/5h 两段总和 40m 60m/h =40/60=2/3h 第二段 20m x m/h =2/3-2/5=4/15h 所以，x=20÷4/15=75
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2020-06-22 20:20:49
370073qvc
哪里说了2/3 小时，40 miles 是40英里又不是40分钟
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2020-03-13 12:25:22
akayo回复370073qvc
速度要每小时60mile ，那40mile不就是要花40/60小时吗，也就是40分钟
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2020-08-24 08:10:51
164616bgqi
呵呵呵竟然不是70！！
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2019-12-26 14:34:00
Mandydydy
呵呵呵竟然不是70！！
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2019-12-13 12:18:08
sweetymiley
呵呵呵竟然不是70！！
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2019-09-15 17:14:32
Vikkii
呵呵呵竟然不是70！！
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2019-05-17 14:00:47
Pioggia
呵呵呵竟然不是70！！
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2019-03-28 12:29:37
gmat801
呵呵呵竟然不是70！！
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2018-09-10 08:14:50
xmdhappy
呵呵呵竟然不是70！！
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2018-08-12 12:44:14
糖糖要加油
呵呵呵竟然不是70！！
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2018-01-17 20:47:42
花枝春野
竟然不是70！！！
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2017-10-28 19:32:18
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问题求解PS
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