What is Elapsed Time?
Basics on the topic What is Elapsed Time?
Elapsed Time
Freddie receives a letter from Zuri one day about a scavenger hunt. He needs to follow all of the clues to get a surprise at the end! However, he needs to make sure he gets to all of the clues in time for his surprise. In order to do this Freddie will need to use elapsed time strategies and elapsed time using a number line. Read more below to learn more about how to find elapsed time.
What is Elapsed Time?
What’s elapsed time? Have you ever wondered “what does elapsed time mean?” Elapsed time or time elapsed is how long an activity takes from beginning to end. In this video we explore how to calculate elapsed time using a number line. We can also find this by measuring elapsed time.
How to Determine Elapsed Time
To find elapsed time, always begin by putting the start time on the LEFT side of the number line. Next, we can put our end time on the RIGHT side of the number line. Then, skip count, or count forward until you reach the end time. When skip counting with time it can be helpful to skip count by the largest unit of time first.
Elapsed Time – Examples
Take a look at the elapsed time number line below. It shows the starting time one the right side of the number line. It also has the end time on the left side of the number line. We can calculate elapsed time using skip counting on the number line. If we skip count forward small amounts we find that the time elapsed is fortyfive minutes.
Elapsed Time – Practice
Your turn! Try calculating the number line elapsed time on the problem below.
Freddie left his house at 6:45 and got to his friend’s house at 7:20, how much time has elapsed? Remember that elapsed time is how long an event lasts from beginning to end. These are the steps you can take to find how much time has elapsed:
Step #  What to do 

1  Put the starting time on the left side of the number line. 
2  Put the end time on the right side of the number line. 
3  Skip count forward small amounts until you reach the end time. 
4  The amount you counted is the elapsed time. 
The first step is to put the start time on the left side of the number line.
Then put the end time on the right side of the number line.
Next, skip count forward small amounts until you reach the end time.
Well, how much time elapsed from beginning to end?
Thirtyfive minutes have elapsed from beginning to end.
Elapsed Time – Summary
Remember, if you want to find how much time has elapsed, follow these steps to determine elapsed time:
Step #  What to do 

1  Put the starting time on the left side of the number line. 
2  Put the end time on the right side of the number line. 
3  Skip count forward small amounts until you reach the end time. 
4  The amount you counted is the elapsed time. 
After this video, you can find continued practice of elapsed time through elapsed time problems and worksheets.
Transcript What is Elapsed Time?
"Freddie, look at the calendar, do you know what today is?" : "Um... Friday, October the fifteenth?" : "Yes, AND it's the day we leave for Berlin for the birthday party!" : "I totally forgot! You packed the bags, right?" : "Uh oh... I thought that YOU packed the bags." : "What are we going to do? We need to clean, and pack, and I have no idea how long it will take." Freddie and Zuri need to prepare for their trip, and, will need to use "Elapsed Time" to help them complete their tasks. Have you heard of elapsed time before? Elapsed time is how long an activity takes from beginning to end. Today we will explore elapsed time using a number line. Zuri and Freddie need to clean before they start packing. They started cleaning at 11:00 in the morning, and finished at 1:30 in the afternoon. How long did it take for them to clean? We can use elapsed time and a number line to figure this out. Begin by putting the start time, 11:00, on the LEFT side of the number line. Next we can put our end time on the RIGHT side of the number line. Then we can skip count, or count forward, to get to 1:30, our end time. When skip counting with time, start with the largest unit of time to count forward with. We can start by skip counting the hours, from eleven to twelve (...) and from twelve to one. One more hour would put us past the end time (...) so we can continue by skipcounting with minutes. We can skip count by tens, count with me! Ten (...) twenty (...) thirty (...) then we stop because we've reached our end time, 1:30. Now we can add up the time that we counted. First add the hours that we skip counted. How many hours did we skip count here? We skip counted forward two hours. Next, add the minutes that we skip counted, how many minutes did we skip count here? We skip counted forward thirty minutes. If we add those together we will find the elapsed time. That means the elapsed time Zuri and Freddie took to clean was two hours and thirty minutes. After cleaning Freddie and Zuri are tired, but, they still need to pack. Zuri and Freddie started packing at 1:30 and finished at 4:45. How much time elapsed from beginning to end of them packing? We can figure out how long it will take them with elapsed time. Remember to start by putting the start time on the LEFT side of the number line. Which means we will put our end time on the RIGHT side of the number line. Next we can skip count or count forward to get to the end time. We can start by skip counting the hours, twothirty (...) threethirty (...) fourthirty. We will go past our end time if we add another hour, so let's skip count by five minutes now. fourthirty five (...) fourforty (...) fourforty five. Finally we need to count up the time we skip counted to find the elapsed time. We skip counted three hours and fifteen minutes, so Zuri and Freddie took three hours and fifteen minutes to pack. Zuri and Freddie are almost ready to go, but first they need to get their ride ready! This will take them a while because there are many steps. If Zuri and Freddie start preparing their ride at 4:45 and finish at 6:30, how much time has elapsed? It will take Zuri and Freddie one hour and fortyfive minutes to prepare the car. And they are off! Zuri and Freddie have finally begun to travel to the birthday party. They left at 6:45 and finally landed at 8:20, how much time has elapsed? The elapsed time it took Zuri and Freddie to get to their destination is one hour and thirtyfive minutes. : "Phew, we're finally here! I can't wait to see everyone!" : "Uh, Zuri? I have some bad news..." : "I think we went to the wrong Berlin..."
What is Elapsed Time? exercise

Solving the elapsed time.
HintsCount forward in hours first, then in minutes.
Remember to put the start time on the left side of the number line and the finish time on the right side of the number line.
Solution To get from 9:20 to 11:35:
 First, count forward by 1 hour to reach 10:20.
 Then, count forward by another hour to reach 11:20.
 Next, count forward by 10 minutes to reach 11:30.
 Finally, count forward by 5 minutes to reach 11:35.

Arrival time of flights.
HintsFirst, count forward from the start time by 1 hour.
Then, count forward by 30 minutes until you reach the end time.
You might need to break 30 minutes into smaller chunks of time, like 10 minutes.
SolutionIf we use a number line to count forward by one hour, then by 30 minutes, the departure and arrival times would be:
Depart: 4:20 Arrive: 5:50
Depart: 8:25 Arrive: 9:55
Depart: 4:40 Arrive: 6:10
Depart: 10:05 Arrive: 11:35
 For the flight that leaves at 4:40: Add 1 hour to get to 5:40, then add 30 minutes. We need to think of this as 20 minutes to reach 6:00, then another 10 minutes to reach 6:10. In total, 1 hour and 30 minutes has been added on.

How long was the train ride?
HintsRemember that there are 60 minutes in an hour, so we would count 1 hour, or 60 minutes, to get to the next hour.
Remember to first count forward in hours, then in minutes.
You can break up the minutes into smaller chunks to add. For example, 30 minutes could be broken into 20 and 10.
Solution To get from 4:15 to 6:10.
 First, count forward by 1 hour to reach 5:15.
 Then, count on 45 minutes to reach 6:00.
 Finally, count forward 10 minutes to reach 6:10.

How long does each TV show last?
HintsCount forward in hours first from the start time. Then add the minutes in smaller chunks.
When drawing a number line to solve the elapsed time, remember to put the start time on the left side and the end time on the right side.
Solution This image shows a number line to find the elapsed time of Attack of the Really Big Slugs: Start: 2:35 and End: 4:20 = 1 hr 45 mins
 Talent Show: Start: 7:15 and End: 8:35 = 1 hr 20 mins
 Knights and Dragons: Start: 3:55 and End: 5:20 = 1 hr 25 mins
 Super Bowl: Start: 8:30 and End: 10:25 = 1 hr 55 mins

Finding the elapsed time.
HintsRemember that the first thing we do, is to put the start time on the left side of the number line.
Remember to start your jumps in hours.
SolutionPut the start time on the left side of the number line and the end time on the right side of the number line.
Start by counting forward in hours.
Then count forward in minutes.
Count up the total time you skip counted.

The soccer game.
HintsMake sure to add all the times up (the playing, the break, and the injury time) to find how long the game lasted in total.
If we took off the injury time, that means that the game would finish 5 minutes earlier.
Solution In addition to the playing time, there was a halftime break and injury time of 20 minutes total added on.
 The whole game finished at 9:20pm.
 If it hadn't been for the injury, they would have finished at 9:15pm.
 Last week they went to a game that had no injury time. The game was 105 minutes long, or 1 hour and 45 minutes.
 It started at 2:40pm and finished at 4:25pm.
 After that game, they went to get the bus home and only had 20 minutes to catch it, as it left at 4:45pm.
 They were on the bus for 1 hour and 20 minutes, so they finally got off the bus at 6:05pm.