Let’s Learn to Find Elapsed Time
Goal:
Goal:
How do you find elapsed time?
We can learn how to find elapsed time! Elapsed time is how much time has gone by. Let’s see what it looks like on a clock when 1 hour has elapsed.
Look at the clock below. Click it to see one hour elapse.
You can see that the hour hand moves from the 8 to the 9. We can count up from 8 to 9 to know that 1 hour has elapsed. We can also subtract to find the elapsed time! We can subtract the end time from the beginning time to find the elapsed time.
9 \({ - }\) 8 \({ = }\) 1
Subtracting helps us find the elapsed time! Click through the slides below to practice finding the elapsed time.
Mateo the firefighter has a meeting that starts at 2:30 pm. Look at the clock below to see what time the meeting starts.
Now, look at the clock below to see what time his meeting ended.
The meeting is over at 3:30. To find the elapsed time, we can subtract! Start with the end time and subtract the starting time, like this:
3:30 \({ - }\) 2:30 \({ = }\) 1
The minutes subtract to zero because 30 take away 30 equals zero. Then we subtract the hours 3 \({ - }\) 2 \({ = }\) 1. One hour has elapsed!
Now, Mateo needs to go to the store to pick up equipment they need at the firehouse. He returns at 5:00, and 1 hour has elapsed.
How do we know what time Mateo left the firehouse? We need to start at the ending time, 5:00, and subtract 1 hour.
5 \({ - }\) 1 \({ = }\) ?
What time did Mateo leave the firehouse?
4:00 pm
When Mateo returns at 5:00 pm, he puts ingredients for stew in a pot and sets the timer for 6:00. How much time will elapse before dinner is ready?
We can subtract to find the answer. We start with the end time and subtract the starting time.
6 \({ - }\) 5 \({ = }\) ?
How much time will elapse until dinner is ready?
1 hour
Excellent!
After the firefighters finish dinner and clean up, they decide to watch a movie. They start the movie at 7:00 pm.
The movie ends at 9:00.
Let’s subtract to find the elapsed time.
9 \({ - }\) 7 \({ = }\) 2
Two hours have gone by!
The firefighters are used to staying up late, so they aren’t ready to go to bed after the movie. They decide to play cards! They start their card game at 9:00 pm.
They finish playing cards at 12:00, midnight.
How can we find out how much time has elapsed while they played cards? We can subtract! Start with the ending time, and take away the beginning time.
12 \({ - }\) 9 \({ = }\) ?
How much time elapsed while they were playing cards?
3 hours
Now, the firefighters are tired and ready for bed. But they don’t sleep for very long! The fire alarm sounds, and they are off to the rescue. The firefighters leave the fire station at 1:30 am. They stop the fire and are back at the station at 4:30 am. How much time has elapsed?
Start with the ending time, and subtract the starting time.
4:30 \({ - }\) 1:30 \({ = }\) 3
Yes! Three hours have passed because 30 \({ - }\) 30 is zero and 4 \({ - }\) 1 \({ = }\) 3.
You are doing a great job finding elapsed time!
The firefighters go back to bed at 5:00 am. They wake up at 7:00 am. How much time has elapsed?
- 2 hours
- 1 hour
- 3 hours
Correct!
Incorrect. We start on hour 5 and end on 7. How much do you need to add to 5 to get 7?
Incorrect. We start on hour 5 and end on 7. How much do you need to add to 5 to get 7?
Summary
Questions answered correctly:
Questions answered incorrectly: