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【OG20-P173-173题】
The light in a restroom operates with a 15-minute timer that is reset every time the door opens as a person goes in or out of the room. Thus, after someone enters or exits the room, the light remains on for only 15 minutes unless the door opens again and resets the timer for another 15 minutes. If the times listed above are the times at which the door opened from 8:00 to 10:00, approximately how many minutes during this two-hour period was the light off?
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当前版本由 700+冲冲冲!!! 更新于2020-03-25 22:00:27 感谢由 700+冲冲冲!!! 对此题目的解答所做出的贡献。8.31-8.54 off 8mins
9.11-9.29 off 3mins
9.31-10.00 off 14mins
因此是25mins
题目意思:
是问你关灯的时长多少min
条件是:开门或者关门,灯会打开,如果开门或关门中间间隔了15min灯会自动熄灭
(1) 可以看出来8:00-8:31灯一直开着(因为总是没有到15分钟就有人用厕所)
(2) 8:31-8:54 这个期间间隔23min,灯15min自动熄灭,也就是说在8:46的时候熄灭,到再次有人来(灯打开),这个熄灭的时长是8min
(3) 8:54-9:11灯一直开着(理由如(1))
(4) 9:11-9:29 间隔时长为18min,灯灭时长为18-15=3min
(5) 9:29-9:31灯一直开着
(6) 9:31-10:00 间隔时长29min,灯灭时长为29-15=14min
(7) 总时长 = 8 + 3 + 14 = 25min
题目讨论 (2条评论)

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373961gg
漏算9:31-10:00的时间 = =
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0 回复 2020-05-20 10:45:38
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emily666回复373961gg
考场一紧张,更加容易漏看。。。
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0 回复 2020-06-02 17:16:54
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你这只猪回复373961gg
复盘再看这道题,第一次做对,第二次竟然算不出正确答案,漏看了9:31-10:00真的是太可恶了
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0 回复 2020-06-26 14:07:07
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EricaWu
题目大致意思是:每当有人进出,灯会自动亮15分钟,如果15分钟内又有人进出,则重新计时。
求:两个小时灯灭的时间是多久?
解:第一步是找到大于15分钟的时间段,
由图可知,大于15分钟的共有3个时间段:8:31~8:54,9:11~9:29,9:31~10:00
则灯灭的时间为超过15分钟的所有时间段各减去相应的15分钟亮灯时间,即:(54-31)+(29-11)+(60-31)-15*3 = 25 mins
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0 回复 2018-02-09 14:31:49