Elapsed Time (Grade 4)
Elapsed time is the amount of time that passes between a start time and an end time. If a movie starts at 3:00 PM and ends at 5:15 PM, the elapsed time is 2 hours 15 minutes.
In Class 4, you will learn to calculate elapsed time, find end times, and find start times.
What is Elapsed Time - Class 4 Maths (Time)?
Elapsed time = End time − Start time. It tells you how long something lasted.
Three types of elapsed time problems:
- Given start and end time → find duration.
- Given start time and duration → find end time.
- Given end time and duration → find start time.
Elapsed Time (Grade 4) Formula
Elapsed Time = End Time − Start Time
End Time = Start Time + Duration
Start Time = End Time − Duration
Counting-on method: Count from the start time to the end time in steps — first count to the next full hour, then count the remaining hours and minutes.
Solved Examples
Example 1: Example 1: Finding elapsed time
Problem: School starts at 8:30 AM and ends at 2:45 PM. How long is the school day?
Solution:
Step 1: From 8:30 AM to 2:30 PM = 6 hours.
Step 2: From 2:30 PM to 2:45 PM = 15 minutes.
Step 3: Total = 6 hours 15 minutes.
Answer: The school day is 6 hours 15 minutes.
Example 2: Example 2: Finding end time
Problem: Aman starts his homework at 4:20 PM. He works for 1 hour 35 minutes. When does he finish?
Solution:
Step 1: 4:20 PM + 1 hour = 5:20 PM.
Step 2: 5:20 PM + 35 minutes = 5:55 PM.
Answer: Aman finishes at 5:55 PM.
Example 3: Example 3: Finding start time
Problem: A train arrives at 11:10 AM. The journey took 2 hours 40 minutes. When did it depart?
Solution:
Step 1: 11:10 AM − 2 hours = 9:10 AM.
Step 2: 9:10 AM − 40 minutes = 8:30 AM.
Answer: The train departed at 8:30 AM.
Example 4: Example 4: Crossing noon
Problem: A cooking show starts at 11:45 AM and ends at 1:15 PM. What is the elapsed time?
Solution:
Step 1: From 11:45 AM to 12:00 noon = 15 minutes.
Step 2: From 12:00 noon to 1:15 PM = 1 hour 15 minutes.
Step 3: Total = 15 min + 1 hr 15 min = 1 hour 30 minutes.
Answer: The show is 1 hour 30 minutes long.
Example 5: Example 5: Using the counting-on method
Problem: Priya starts reading at 6:50 PM and stops at 8:25 PM. How long did she read?
Solution:
Step 1: 6:50 → 7:00 = 10 minutes (count to the next hour).
Step 2: 7:00 → 8:00 = 1 hour.
Step 3: 8:00 → 8:25 = 25 minutes.
Step 4: Total = 10 min + 1 hr + 25 min = 1 hour 35 minutes.
Answer: Priya read for 1 hour 35 minutes.
Example 6: Example 6: Bus travel
Problem: Kavi boards the bus at 7:15 AM. The ride takes 55 minutes. When does he reach?
Solution:
Step 1: 7:15 + 45 minutes = 8:00 AM.
Step 2: 55 − 45 = 10 minutes still remaining.
Step 3: 8:00 + 10 = 8:10 AM.
Answer: Kavi reaches at 8:10 AM.
Example 7: Example 7: Cricket match
Problem: A cricket match starts at 9:30 AM and lasts 3 hours 15 minutes with a 30-minute lunch break. When does it end?
Solution:
Step 1: Total time = 3 hr 15 min + 30 min = 3 hr 45 min.
Step 2: 9:30 AM + 3 hours = 12:30 PM.
Step 3: 12:30 PM + 45 minutes = 1:15 PM.
Answer: The match ends at 1:15 PM.
Example 8: Example 8: How long until?
Problem: It is 3:40 PM now. Aditi's art class starts at 5:00 PM. How long does she have to wait?
Solution:
Step 1: 3:40 → 4:00 = 20 minutes.
Step 2: 4:00 → 5:00 = 1 hour.
Step 3: Total = 1 hour 20 minutes.
Answer: Aditi waits for 1 hour 20 minutes.
Example 9: Example 9: Late arrival
Problem: Rahul's school assembly starts at 8:00 AM. He arrives at 8:23 AM. How late is he?
Solution:
Step 1: 8:23 − 8:00 = 23 minutes.
Answer: Rahul is 23 minutes late.
Key Points to Remember
- Elapsed time = End time − Start time.
- Use the counting-on method: count to the next full hour, then count remaining hours and minutes.
- When time crosses noon (12:00), count AM to 12:00, then 12:00 to PM time.
- To find end time: add the duration to the start time.
- To find start time: subtract the duration from the end time.
- If minutes exceed 60 when adding, carry over to hours.
Practice Problems
- A movie starts at 4:30 PM and ends at 7:00 PM. How long is it?
- Meera starts cooking at 6:45 PM. It takes 1 hour 25 minutes. When is dinner ready?
- A bus arrives at 10:15 AM after a 2 hour 30 minute journey. When did it leave?
- How much time passes from 11:40 AM to 2:10 PM?
- Dev leaves home at 7:50 AM and reaches school at 8:35 AM. How long is his journey?
- A TV show starts at 8:15 PM and lasts 45 minutes. When does it end?
- Neha's train departs at 6:55 AM and arrives at 9:20 AM. What is the travel time?
Frequently Asked Questions
Q1. What is elapsed time?
Elapsed time is the amount of time that passes from a start time to an end time. It tells you how long something lasted.
Q2. How do you calculate elapsed time?
Subtract the start time from the end time. Use the counting-on method: count forward from the start to the next full hour, then count the remaining hours and minutes to the end time.
Q3. What is the counting-on method?
Count forward in steps: first from the start time to the nearest full hour, then count full hours, then count remaining minutes. Add all the pieces together.
Q4. How do you find the end time?
Add the duration to the start time. If the minutes total more than 60, convert the extra minutes to hours.
Q5. How do you find the start time?
Subtract the duration from the end time. If you cannot subtract the minutes, borrow 1 hour (= 60 minutes).
Q6. What happens when elapsed time crosses 12 noon?
Count from AM to 12:00 noon, then from 12:00 to the PM time. Add the two parts. For example, 11:30 AM to 1:15 PM = 30 min + 1 hr 15 min = 1 hr 45 min.
Q7. Can elapsed time be more than 24 hours?
Yes, if the event spans more than a day. Count the hours or convert to days and hours.
Q8. What is the difference between elapsed time and clock time?
Clock time tells you what the current time is (e.g., 3:45 PM). Elapsed time tells you how much time has passed between two clock times (e.g., 2 hours 30 minutes).
