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 skip-counting 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, two-thirty (...) three-thirty (...) four-thirty. We will go past our end time if we add another hour, so let's skip count by five minutes now. four-thirty five (...) four-forty (...) four-forty 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 forty-five 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 thirty-five 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..."