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  • - [Instructor] We are told that Andre goes to a movie

  • that starts at 19 hours 45 minutes,

  • or 19:45,

  • and is 90 minutes long.

  • What time is the movie finished?

  • So pause this video, and see if you can answer that

  • before we work through it together.

  • All right, so what I like to do is set up

  • what we could call a timeline.

  • So if this is our timeline,

  • and let's say that this is 19 hours right over here,

  • 19 hours,

  • maybe this is 20 hours right over there,

  • and then this would be 21 hours right over there.

  • Now, what time does the movie start?

  • It starts at 19 hours 45 minutes.

  • So this would be 19 hours 30 minutes,

  • which would be halfway between 19 hours and 20 hours,

  • and 19 hours 45 minutes

  • would be halfway between 19:30 and 20.

  • So 19 hours and 45 would be right over there.

  • So let me write that down.

  • That is 19 hours and 45 minutes,

  • and that is when this movie is going to start.

  • Now, it's going to continue for 90 minutes.

  • So when does it end?

  • So there's a couple of ways you could think about it.

  • The way I think about it is it will take us 15 minutes

  • to get to 20 hours, so that's 15 minutes.

  • And so 15 minutes of the movie has happened by 20 hours.

  • And then how much is left?

  • Well, 19 minus 15 is 75,

  • so then there's another 75 minutes left.

  • Well, 60 of those 75 are gonna get you to the next hour,

  • so then it's going to be like this.

  • So then you're going to have another 60 minutes

  • to get to the next hour.

  • So, so far we've used 75,

  • and then you're going to need another 15 minutes

  • to have a total of 90 minutes.

  • So then you're going to have another 15 minutes.

  • And so when does the movie end?

  • Well, as you can see, we started at 19:45,

  • 15 minutes got us to 20,

  • another 60 minutes got us to 21,

  • so now we have a total of 75.

  • And then another 15 would give us a total of 90,

  • so we are finishing 15 minutes

  • after the 21st hour

  • or after hour 21 or however you wanna think about it.

  • So this time right over here is going

  • to be 21 hours and 15 minutes,

  • or 21:15.

  • So that's the time that the movie is finished.

- [Instructor] We are told that Andre goes to a movie

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在24小時內找到電影的結束時間|數學|可汗學院 (Finding the end time for a movie in 24 hour time | Math | Khan Academy)

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    林宜悉 發佈於 2021 年 01 月 14 日
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