Calculating Elapsed Time

Clocks and time are all around us. It's something that we use every single day. How do you know how much time has passed? That is something called elapsed time. And that is what we're going to learn today. Let's get into it. Doodly doodle doodly doodle doodly Doodles and Digits. Area. Symmetry. Fractions too. It's all here for you. All right. So what is elapsed time? Elapsed time is the amount of time that passes between the beginning and the end of an event. Why is elapsed time important? It's really important because think about for example even school. You get to school at certain time and so much time has passed until you get to go home. If you don't know about elapsed time, you might not know what time you need to schedule things. You might not even know how much time you have in the afternoon to play your favorite sport or hang out with your friends. If you aren't sure how to tell time in general, before you go on to trying to figure out elapsed time, check out our other video that actually shows you how to tell time with an analog clock. So how do you tell elapsed time? There's couple different ways that you can tell elapsed time. Let me show you the first way. Your dance class starts at 6:15 p.m. and is one hour and 30 minutes long. What time will your dance class be over? I'm going to use the number line. First, let's draw the number line. We know that dance class starts at 6:15 p.m., so let's place that here. We also know that the class is one hour and 30 minutes long. Let's use the number line to break that down into easier chunks to add. First I'm going to add one hour to 6:15. That will be 7:15 p.m.. Now let's add ten minutes. So we'll be at 7:25 p.m., another ten minutes, 7:35 p.m., and one more ten minutes, 7:45 p.m.. So we actually added total of 30 minutes. What did we land on? We landed at 7:45 and that is our answer. All right. Let's look at this situation here. You have dentist appointment. That dentist appointment starts at 1:30 and they tell you that your appointment is going to last 45 minutes. What time will you be done with your dentist appointment? And what time does someone need to come pick you up? love looking at clock to help me visually see how much time has passed. Let's look at this clock. So the dentist appointment starts at 1:30, and they tell me it's going to last 45 minutes. Let's move 45 minutes on the clock. clock can be helpful tool to try to figure out what time has passed, and also what time will be at the end of whatever event you're having. So we're going to move 45 minutes. Okay. 45 minutes past 1:30. What do we land on in the clock? You're right. It's 2:15. So someone would need to pick you up at the dentist at 2:15. Let's try another method. Let's say that your lunch time starts at 12:20. You get 30 minutes for lunch. What time will your lunch be over? Let's make t-chart to solve this. All right. We're going to start at 12:20 and each time we break up that 30 minutes, we'll put the elapsed time in the right column. We'll go by ten minutes. 12:20 plus ten minutes is 12:30, 12:30 plus ten minutes is 12:40 and 12:40 plus ten minutes is 12:50. So we've added 30 minutes of elapsed time to equal our final time, which is. 12:50. Your lunch will be over at 12:50 p.m.. Let's do few more together. Liam is going on plane ride. The plane leaves at 3:40 p.m. and is four hours and 30 minutes long. What time will his plane land? Let's draw another number line. All right. We're going to start at 3:40 p.m. and break down the four hours and 30 minutes, because we know that's how long his flight will be. Let's start with the hours. I'm going to start at 340 and jump. One hour. Two hours. Three hours and four hours. What did we land on? Now I'm going to add 30 minutes and ten minute increments. Ten minutes. Another ten minutes and another ten minutes. What time will his plane land? 8:10 p.m.. Let’s try another one. Jamal's basketball practice starts at 3:15 p.m. and ended at 4:40 p.m.. How much time did Jamal spend at practice? Let's use chart. I'm going to start at 3:15, and know my end time needs to be 4:40. So how much time are we going to add in the right column to get to 4:40 p.m.? I'll first add an hour to get to 4:15. Now I'm going to do it in ten minute increments, so I'll have 4:25, 4:35. Look, only have five more minutes to get to our end time. So we know that Jamal spent one hour and 25 minutes at practice. Did you get it correct? Now that we've done couple problems together trying to find elapsed time. Let's see if you can do few on your own. Make sure you take your time. Use whatever strategy works best for you. Grab clock or just some paper to try to see if you can figure out these problems. The class left for field trip at 9:15 a.m. and returned at 12:45 p.m.. How long were they gone? All right. I'll draw number line to show my thinking. We start at 9:15 a.m.. I'm going to make hour jumps until we get to 12. So we have nine plus one hour is 10:15 a.m., plus another hour, which is 11:15, plus another hour, which is 12:15. Now I'm going to add in ten minute increments. 12:15 plus ten minutes is 12:25 plus another ten minutes, 12:35 and another ten minutes is 12:45. So we know that the amount of time that passed was three hours and 30 minutes. Sophia started soccer practice at 4:30 p.m. Her practice is two hours and 20 minutes long. What time does her practice end? All right. I'm going to use the chart method to solve this problem. We know that her practice starts at 4:30 and we're going to add on two hours and 20 minutes. But we'll break it down so it's little easier to add. 4:30 plus one hour is 5:30. 5:30 plus another hour is 6:30. Now we're going to add on ten minutes. So that is 6:40 and another ten minutes which is 6:50. The time that her practice is over is at 6:50. Did you get it correct? All right. How do you do? Are you pro at elapsed time now? Make sure you check out our other math videos. Bye!