An Intro to Elapsed Time Using a Clock | Math with Mr. J

追加: 2026-05-27

[00:00:00]Welcome to Math with Mr. J.

[00:00:04]In this video, I'm going to go through an introduction to elapsed time. Now, what is elapsed time? Well, elapsed time is the amount of time that passes from the start of an event to the end. So, basically, elapsed time is how much time something takes. Again, how much time passes from start to end. Now, we use time and think about time every day. So, this is something that's really important to understand. Let's take a look at our first situation here. Sophia started cleaning her room at 1:00 p.m.

[00:00:44]Sophia was done cleaning at 1:15 p.m.

[00:00:48]She cleaned for 15 minutes. So, when it comes to elapsed time, we'll always have a start time, an end time, and then the elapsed time. In some situations, we'll need to figure out the elapsed time. In other situations, we'll need to figure out the start time and then in others, the end time. We'll go through an example of each in this video. For this example, the start time, end time, and elapsed time were all given just so we can see what these all mean. And we have everything laid out here to help us stay organized. The start time is 1 p.m. The end time is 1:15 p.m. Now, how much time elapsed? How much time passed from the start to the end of her cleaning? Well, she cleaned for 15 minutes. That's the elapsed time.

[00:01:49]The amount of time that passed from the start to the end. Another quick example.

[00:01:54]Let's say you start a movie at 400 p.m.

[00:01:58]and it ends at 6:00 p.m. The elapsed time would be 2 hours. Now, in this video, we're just going to focus on minutes and go through a few different situations in order to start building a nice understanding of elapsed time.

[00:02:17]Let's jump into number one. Taking a look at number one, we have Miley started eating lunch at 12:15 p.m. She ended her lunch at 12:35 p.m. How long was Miley's lunch? In this situation, we know our start time 12:15 p.m. and end time 12:35 p.m. So, start time 12:15 p.m. and end time 12:35 p.m.

[00:02:48]So, we need to figure out the elapsed time. How long was Miley's lunch? We're going to use the clock to the right to help us think through this. The clock is showing 12:15. the start time with the end time being 12:35 that means the minute hand will be pointing at the seven. So right here now I do want to mention there are different ways to think through elapsed time. There are different strategies we can use and the more you work with time the better you'll get at these. So I'll go through a few different ways to think through this one. Now, going from 12:15 to 12:35, we need to see how many minutes from the minute hand pointing to the three to the minute hand pointing to the 7. Can we count each individual minute here and count by ones? Sure. But that's not the best way to go about this. That will make this harder and longer than it needs to be. One strategy we can use is to count by fives. So, starting at 12:15 here, we have 5 minutes, 10 minutes, 15 minutes, and 20 minutes to get to 12:35. So, 5 minutes + 5 minutes + 5 minutes + 5 minutes again gives us 20 minutes. So, Miley's lunch was 20 minutes long. Now, let's clear that and think through this another way. Could we count by tens? Sure. So maybe you're thinking, okay, we have 10 minutes, 20 minutes. So 10 minutes plus 10 minutes gives us 20 minutes as well.

[00:04:40]Let's clear that and do one more strategy. Now, for our last strategy here, if you're really starting to understand time, you may think, well, it takes 15 minutes to go from 12:15 to 12:30, and then we have another five to get to 12:35.

[00:05:02]So, 15 minutes plus 5 minutes gives us that 20 minutes as well. So, our elapsed time here, 20 minutes. So, a few different strategies there, a few different ways to think through this. Now, if you're just starting out, feel free to just count by fives to make things simple, and you can work your way up to other strategies.

[00:05:31]Use what works best for you. Let's move on to number two. Taking a look at number two, we have Nikolai started working out at 6:50 a.m. He worked out for 35 minutes. What time did his workout end? So, here we have the start time, 6:50 a.m. So, 6:50 in the morning, and he worked out for 35 minutes. That's the elapsed time, how long his workout lasted. We need to figure out the end time. So, what time his workout ended?

[00:06:11]Let's use the clock to help us out. It's showing our start time of 6:50 a.m. So, we need to think about that minute hand moving forward 35 minutes. Again, there are different ways to think through this. I'll go through two here for this example. The first, let's start by counting by fives. So five minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes. So counting by fives again, we have 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes. So in 35 minutes, the minute hand is going to be pointing to the five. That means our end time is 6:25 a.m., right? Well, if he started at 6:50 a.m., would it make sense that he ended at 6:25 a.m.? No, that doesn't make sense. This is not correct. Think about it. When the minute hand hits 12, we start a new hour. So, this is now 7:00, 7 a.m., then the minute hand goes all the way to the 5. So, we pass 7 a.m. and go to 7:25 a.m. And that's our end time. Let's clear that and I'll show you another strategy. Now, another strategy here is to use 7:00, 7 a.m., meaning we see that we have 10 minutes until 7 a.m. So, we're hitting that next hour exactly, and then we go from there. So, we have 10 minutes and then we need another 25 minutes to give us that total of 35 minutes. So, we have 10 minutes. That brings us to 7:00 a.m. exactly. Then we have another 25 minutes to give us that total of 35 minutes. And in 35 minutes, the minute hand is going to be pointing to the five. So the end time here is 7:25 a.m.

[00:08:47]So we used that exact hour to break this up. Using exact hours makes things simpler to work with. So this is a good strategy to start thinking about. Now, like I mentioned in number one, if you're just starting out, and some of these strategies are a little confusing, just start by counting by fives until you feel more and more comfortable, and you'll start getting better and better at this. Let's move on to number three.

[00:09:18]Taking a look at number three, we have James stopped reading at 4:45 p.m. He read for 25 minutes. What time did he start reading? So, here we have our end time, 4:45 p.m., and then our elapsed time, 25 minutes. That's how long he read for. We need to figure out the start time. So, we're actually going to work backwards using the clock. The clock is showing the end time of 4:45 p.m. We need to go back 25 minutes to see what time James started reading.

[00:09:58]Again, the clock is showing the end time, so we need to go back 25 minutes.

[00:10:05]Let's start by counting by fives. So, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes. So just to double check here, we have 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes. That means for our start time here, the minute hand is pointing to the four.

[00:10:34]James started reading at 4:20 p.m. Let's clear that and take a look at another way to think through this. Now, another strategy here could be to use 4:30. Just like we talked about using exact hours in number two, using half past an hour can be helpful as well. So, for this example, we would go back 15 minutes to get to 4:30. And then in order to get to that 25 minutes, we need to go back another 10 minutes. And that brings our minute hand to the four. So we get 4:20 p.m.

[00:11:17]that way as well. And that's our start time. So again, 4:20 p.m. So to recap that strategy, we went back 15 minutes to start. That brought us to 4:30. Then we went another 10 minutes to get to that total of 25 minutes. And that brought us to 420. So there you have it. There's an introduction to elapsed time. I hope that helped.

[00:11:51]Thanks so much for watching.

[00:11:54]Until next time, peace.