Elapsed Time Word Problems
Elapsed time is the amount of time that passes between a start time and an end time. You use elapsed time every day — to find out how long a class lasts, how much time is left before lunch, or how long a journey took.
In Class 4, you will solve word problems that involve finding the elapsed time, the end time, or the start time. You will work with hours and minutes using both 12-hour and 24-hour clock formats.
What is Elapsed Time Word Problems - Class 4 Maths (Time)?
Elapsed time is the difference between the end time and the start time.
Elapsed Time = End Time − Start Time
Three types of problems:
- Find elapsed time: Given start and end time → subtract.
- Find end time: Given start time and duration → add.
- Find start time: Given end time and duration → subtract.
Elapsed Time Word Problems Formula
End Time = Start Time + Elapsed Time
Start Time = End Time − Elapsed Time
Key conversions:
- 1 hour = 60 minutes
- 1 day = 24 hours
- When minutes exceed 60, convert: 75 minutes = 1 hour 15 minutes
Solved Examples
Example 1: Example 1: Finding elapsed time
Problem: Ria's dance class starts at 4:15 PM and ends at 5:45 PM. How long is the class?
Solution:
Step 1: Hours: 5 − 4 = 1 hour
Step 2: Minutes: 45 − 15 = 30 minutes
Answer: The dance class is 1 hour 30 minutes long.
Example 2: Example 2: Finding end time
Problem: Aman starts his homework at 6:20 PM. He works for 1 hour 45 minutes. What time does he finish?
Solution:
Step 1: Add hours: 6:20 + 1 hour = 7:20 PM
Step 2: Add minutes: 7:20 + 45 minutes = 8:05 PM (20 + 45 = 65 minutes = 1 hour 5 minutes → 7 + 1 = 8 hours, 5 minutes)
Answer: Aman finishes at 8:05 PM.
Example 3: Example 3: Finding start time
Problem: A movie ends at 9:10 PM. It was 2 hours 25 minutes long. What time did it start?
Solution:
Step 1: Subtract hours: 9:10 − 2 hours = 7:10 PM
Step 2: Subtract minutes: 7:10 − 25 minutes. Since 10 < 25, borrow 1 hour: 6:70 − 25 = 6:45 PM
Answer: The movie started at 6:45 PM.
Example 4: Example 4: Elapsed time crossing noon
Problem: Dev's school starts at 8:30 AM and ends at 2:15 PM. How long is the school day?
Solution:
Step 1: From 8:30 AM to 12:00 PM = 3 hours 30 minutes
Step 2: From 12:00 PM to 2:15 PM = 2 hours 15 minutes
Step 3: Total = 3 hours 30 minutes + 2 hours 15 minutes = 5 hours 45 minutes
Answer: The school day is 5 hours 45 minutes long.
Example 5: Example 5: Bus journey
Problem: Meera boards a bus at 10:40 AM and reaches home at 12:05 PM. How long is the journey?
Solution:
Step 1: From 10:40 to 11:00 = 20 minutes
Step 2: From 11:00 to 12:00 = 1 hour
Step 3: From 12:00 to 12:05 = 5 minutes
Step 4: Total = 1 hour 25 minutes
Answer: The journey is 1 hour 25 minutes.
Example 6: Example 6: Train timing
Problem: A train departs at 7:50 AM and the journey takes 4 hours 35 minutes. At what time does it arrive?
Solution:
Step 1: 7:50 + 4 hours = 11:50 AM
Step 2: 11:50 + 35 minutes = 12:25 PM (50 + 35 = 85 min = 1 hr 25 min → 12:25)
Answer: The train arrives at 12:25 PM.
Example 7: Example 7: Cooking time
Problem: Priya puts a cake in the oven at 3:45 PM. It needs to bake for 50 minutes. At what time should she take it out?
Solution:
Step 1: 3:45 + 50 minutes = 3:95. Since 95 > 60, convert: 95 − 60 = 35 minutes, add 1 hour → 4:35 PM
Answer: Priya should take the cake out at 4:35 PM.
Example 8: Example 8: Multiple activities
Problem: Arjun goes swimming from 5:00 PM to 5:45 PM, then plays cricket from 5:45 PM to 7:00 PM. What is his total activity time?
Solution:
Step 1: Swimming: 5:45 − 5:00 = 45 minutes
Step 2: Cricket: 7:00 − 5:45 = 1 hour 15 minutes
Step 3: Total = 45 min + 1 hr 15 min = 2 hours
Answer: Arjun's total activity time is 2 hours.
Example 9: Example 9: Elapsed time in minutes only
Problem: An exam starts at 10:15 AM and lasts 90 minutes. When does it end?
Solution:
Step 1: 90 minutes = 1 hour 30 minutes
Step 2: 10:15 + 1 hour = 11:15 AM
Step 3: 11:15 + 30 minutes = 11:45 AM
Answer: The exam ends at 11:45 AM.
Example 10: Example 10: Finding the longer activity
Problem: Aditi reads from 4:30 PM to 5:50 PM. Neha reads from 6:10 PM to 7:20 PM. Who reads for a longer time?
Solution:
Step 1: Aditi: 5:50 − 4:30 = 1 hour 20 minutes
Step 2: Neha: 7:20 − 6:10 = 1 hour 10 minutes
Step 3: 1 hr 20 min > 1 hr 10 min
Answer: Aditi reads for longer by 10 minutes.
Key Points to Remember
- Elapsed time = End time − Start time.
- To find the end time, add the duration to the start time.
- To find the start time, subtract the duration from the end time.
- When minutes go above 60, convert to hours: 75 min = 1 hour 15 min.
- When subtracting and minutes are not enough, borrow 1 hour = 60 minutes.
- Break problems crossing noon (AM to PM) into two parts — to 12:00 and then from 12:00.
- 1 hour = 60 minutes, 1 day = 24 hours.
Practice Problems
- A cricket match starts at 2:30 PM and ends at 5:15 PM. How long is the match?
- Kavi starts reading at 7:10 AM and reads for 1 hour 35 minutes. At what time does he stop?
- A train arrives at 4:50 PM. The journey took 3 hours 20 minutes. When did the train leave?
- Dev's school starts at 8:15 AM and ends at 1:45 PM. How many hours and minutes is the school day?
- Meera puts milk on the stove at 6:35 PM. It boils in 25 minutes. What time does it boil?
- An exam starts at 9:30 AM and lasts 2 hours 15 minutes. What time does it end?
- Ria walks from 5:40 PM to 6:25 PM. How many minutes does she walk?
Frequently Asked Questions
Q1. What is elapsed time?
Elapsed time is the amount of time that passes from the start of an event to the end. It is calculated by subtracting the start time from the end time.
Q2. How do you calculate elapsed time when the times cross noon?
Split the calculation into two parts: first find the time from start to 12:00 PM, then from 12:00 PM to the end time. Add the two parts together.
Q3. What do you do when you need to subtract minutes but the end time has fewer minutes?
Borrow 1 hour from the hours column and add 60 to the minutes. For example, to subtract 40 minutes from 3:15, convert to 2:75 and then subtract 40 to get 2:35.
Q4. How do you convert minutes to hours and minutes?
Divide the total minutes by 60. The quotient is hours and the remainder is minutes. For example, 135 minutes = 2 hours 15 minutes (135 ÷ 60 = 2 remainder 15).
Q5. What is the difference between AM and PM?
AM stands for the time from midnight (12:00 AM) to noon (11:59 AM). PM covers noon (12:00 PM) to midnight (11:59 PM). Morning hours are AM and afternoon/evening hours are PM.
Q6. How do you find the end time when given start time and duration?
Add the duration to the start time. First add hours, then add minutes. If the total minutes exceed 60, convert the extra minutes into an additional hour.
Q7. Can elapsed time be in days and hours?
Yes. If the elapsed time exceeds 24 hours, it is expressed in days and hours. For example, 30 hours = 1 day and 6 hours.
Q8. Why is elapsed time useful in daily life?
It helps in planning schedules, estimating travel time, cooking, and managing daily routines. Knowing elapsed time helps you arrive on time and manage tasks efficiently.
