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## Measurement & Data - Statistics & Probability 189-200

### Course: Measurement & Data - Statistics & Probability 189-200>Unit 3

Lesson 3: Elapsed time

# Time differences example

Learn to find the difference between the times shown on two different analog clocks.  Created by Lindsay Spears.

## Video transcript

- [Instructor] We are asked, "How much time has passed "from the time on the left," so right over here, "to the time on the right?" Which we see right over here. And they say that, "The time passed is less than 12 hours." So like always, pause this video and see if you can answer that on your own before we work on this together. All right. So first I just wanna figure out what time is being told by each of these clock faces. So let's go here on the left. So the first thing I'm gonna do is look at the hour hand. And we can see that the hour hand has gone a little bit past six. So it's going to be six-something. Six-something. And then to figure out what the minutes are I can look at the minute hand right over here. And say, "Well, how far has it gone in minutes?" And I like to count by fives because we know when we go from 12 on the clock to one that actually one, two, three, four, five minutes have gone by. And in fact, between any two numbers, it's five minutes. So we go five, 10, 15, 20, 25, 30, 35, 40. And then 41, 42, 43. That's where it's pointing. So it's 6:43, is where we're starting. And then where we're ending, let's see. The hour hand is a little bit past nine. You can see it's past nine. And so it's not necessarily what it's closest to, it's what it's past. So even if the hour hand was like there, even if it was closer to 10 but not quite at 10, you would say, "Okay, it's gonna be nine-something." It's passed nine. And only if it got to 10 or past 10, then you would say, "It's 10-something." So this is gonna be nine-something. And to figure out what that something is, once again, we start here, we can count by fives. Five minutes, 10 minutes, and then we have one more. We get to 11 minutes. So it's 9:11. And they tell us that this is less than 12 hours apart. So it's not like 6:43 in one day, maybe at night, and then 9:11 the next morning. This is maybe the same morning or the same evening. And so we can set up a timeline here. So let's set up a timeline. And so, let's see. The sixth hour is going to be important, so that's six o'clock. And let's see, maybe we wanna go all the way to 10 o'clock. So that we go beyond 9:11. And so then we could say, let's go, have to do seven, eight, and nine. I just wanna get my spacing right. So let's say that this is seven o'clock right over here. This is eight o'clock right over there. And then that is nine o'clock right over there. It's not gonna be a perfect drawing, but this is pretty close. And so let's see. We are starting at 6:43. Which is going to be, let's see, it's going to be roughly, and I just have to say roughly, it's going to be right over there. That's where we are starting. And then 9:11 is going to be roughly right over there. So that is when we are ending. So how much time has gone by? Well, to go from 6:43 to seven o'clock, how many minutes is that? Well, to go from 43 minutes to 60 minutes, you have to add 17 minutes. So this right over here, that is 17 minutes. Just write it out. And then we can see, we have another two hours that goes by from seven o'clock to nine o'clock. So then that's two hours. And then to go from nine o'clock to 9:11, what is going on? Well, that's going to be another 11 minutes. 11 minutes. So how much time has happened? It's going to be 17 minutes plus two hours plus 11 minutes. Well, I find it a little bit easier just to think about the minutes first. So if I add 17 minutes to 11 minutes, 17 plus 11 is 28. I can do that on the side if you want to see it. Seven plus one is eight. One plus one is two. So we are going to have a total of two hours and 28 minutes. And I could write it that way. Two hours, two hours and 28 minutes. And we are done.