Elapsed Time

Grade 3 · Math · Study Guide

Learn how to find elapsed time — how much time passes from a start time to an end time.

Elapsed time is the amount of time that passes between a start time and an end time. To find elapsed time, you count how many minutes or hours pass from when something starts to when it ends.

One strategy is to count on using a number line. Draw a timeline and mark the start time. Then jump by hours, then by minutes, until you reach the end time. Add up all the jumps.

Another strategy is to break the time into parts. For example, if a movie starts at 1:20 and ends at 3:05, count from 1:20 to 2:20 (1 hour), then 2:20 to 3:00 (40 minutes), then 3:00 to 3:05 (5 minutes). Total: 1 hour and 45 minutes.

You can also find an end time if you know the start time and elapsed time: add the elapsed time to the start time. Or find the start time by subtracting elapsed time from the end time.

Always check if you cross over the top of the hour and remember that there are 60 minutes in an hour. Be careful when crossing 12:00, since time goes from 12:59 to 1:00.

Key terms

Elapsed time
The amount of time that passes from a start time to an end time.
Start time
The time when an activity or event begins.
End time
The time when an activity or event finishes.
A.M.
Times from midnight (12:00 AM) to just before noon (11:59 AM).
P.M.
Times from noon (12:00 PM) to just before midnight (11:59 PM).
Number line (for time)
A timeline used to count on by hours and minutes to find elapsed time.

Flashcards

60 minutes = ?
60 minutes = 1 hour
30 minutes = ?
30 minutes = half an hour
Finding elapsed time
Count on from start time to end time using jumps of hours, then minutes.
Finding end time
Add elapsed time to the start time. Start 3:00, add 45 min → End 3:45.
Finding start time
Subtract elapsed time from end time. End 5:30, subtract 1 hr → Start 4:30.
Crossing the hour
Example: 3:50 + 20 min → go to 4:00 (10 min) then add 10 more min → 4:10.
A.M. vs P.M.
A.M. = morning (midnight to noon). P.M. = afternoon/night (noon to midnight).
Elapsed time 9:15 to 11:45
From 9:15 to 11:15 = 2 hours. From 11:15 to 11:45 = 30 minutes. Total: 2 hours 30 minutes.

Questions

  1. A game starts at 2:15 PM and ends at 4:15 PM. How long did the game last?

    1. 1 hour
    2. 2 hours
    3. 3 hours
    4. 30 minutes
    Show answer

    Answer: 2 hours

    From 2:15 to 4:15 is exactly 2 hours. The minutes are the same, so count only the hours: 4 - 2 = 2 hours.

  2. There are 60 minutes in one hour.

    Show answer

    Answer: True

    There are always 60 minutes in one hour. This is a key time fact to remember.

  3. School starts at 8:00 AM. Lunch is 2 hours and 30 minutes later. When is lunch?

    1. 9:30 AM
    2. 10:00 AM
    3. 10:30 AM
    4. 11:00 AM
    Show answer

    Answer: 10:30 AM

    8:00 + 2 hours = 10:00. 10:00 + 30 minutes = 10:30 AM.

  4. A movie starts at 6:00 PM and lasts 1 hour 45 minutes. It ends at ___:___ PM. (Write as H:MM, e.g., 7:45)

    Show answer

    Answer: 7:45

    6:00 + 1 hour = 7:00. 7:00 + 45 minutes = 7:45 PM.

  5. Art class starts at 10:10 AM and ends at 11:00 AM. How long is art class?

    1. 40 minutes
    2. 45 minutes
    3. 50 minutes
    4. 60 minutes
    Show answer

    Answer: 50 minutes

    From 10:10 to 11:00: count from 10:10 to 11:00. 10:10 + 50 minutes = 11:00. Art class is 50 minutes.

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