Lesson 6.2 · Time and Measurement
Elapsed time
Soccer practice starts at 3:15 and ends at 3:52. How long was practice? The time that passes from a start time to an end time is called elapsed time. A number line can help you find it.
Definition
Elapsed time
Elapsed time is how much time passes between a start time and an end time.
Use a timeline
A timeline is a number line for time. Mark the start time. Then make jumps to the end time. Big, friendly jumps are easiest: jump to a time that ends in 0 or 5, or jump to the next hour. Then add up the jumps.
Worked example: How long was practice?
Practice starts at 3:15 and ends at 3:52. How long was practice?
- Jump from 3:15 to 3:50. That is 35 minutes.
- Jump from 3:50 to 3:52. That is 2 minutes.
Add the jumps: . Practice was 37 minutes long.
Crossing the hour
When the time goes past a new hour, make a jump to the hour first. Remember that there are 60 minutes in 1 hour, so 9:40 is 20 minutes away from 10:00.
Worked example: Crossing into a new hour
Art class starts at 9:40 and ends at 10:25. How long is art class?
- Jump from 9:40 to 10:00. That is 20 minutes.
- Jump from 10:00 to 10:25. That is 25 minutes.
Add the jumps: . Art class is 45 minutes long.
Jump to the hour
To find elapsed time, start at the start time and jump to the end time. Jump to the next hour first when you can. Then add all the jumps.
Finding the end time
Sometimes you know the start time and how long something lasts. Then you jump forward to find the end time.
Worked example: When does the movie end?
A short movie starts at 1:35. It lasts 50 minutes. When does it end?
Split 50 into two jumps: 25 minutes gets you to the hour, and minutes are left.
- Jump 25 minutes from 1:35 to 2:00.
- Jump 25 more minutes from 2:00 to 2:25.
The movie ends at 2:25.
Finding the start time
If you know the end time and how long something took, jump backward from the end time.
Worked example: When did swimming start?
Swim lessons end at 5:10. They last 40 minutes. When did they start?
Split 40 into 10 and 30. The 10 gets you back to the hour.
- Jump back 10 minutes from 5:10 to 5:00.
- Jump back 30 more minutes from 5:00 to 4:30.
Swim lessons started at 4:30.
Common mistake
Don't just subtract the minutes when the hour changes. From 9:40 to 10:25, doing gives the wrong answer. An hour has 60 minutes, not 100. Jump to the hour first.
Tip
Check your answer by jumping the other way. If practice lasted 37 minutes from 3:15, then 3:15 plus 37 minutes should land on 3:52. It does!
Practice
Ava starts her homework at 2:10. She finishes at 2:45. How many minutes did she work?
Type a number.
Dinner starts at 6:20. It lasts 25 minutes. What time does dinner end? Write it like 3:52.
Type your answer
A game starts at 11:50 and ends at 12:15. How many minutes long is the game?
Type a number.
The first clock shows when a show starts. The second clock shows when it ends. How many minutes long is the show?
Type a number.
The bus leaves at 7:48. The ride takes 22 minutes. What time does the bus get to school? Write it like 3:52.
Type your answer
Muffins must bake for 18 minutes. They are done at 4:05. What time did they go into the oven? Write it like 3:52.
Type your answer
A baseball game started at 10:25 and ended at 11:10. How long was the game?
Lena starts reading at 3:40. She reads for 15 minutes. Then she draws for 20 minutes. What time does she finish drawing? Write it like 3:52.
Type your answer