Solved Exercises on Elapsed Time to the Nearest Minute in Grade 3

Master elapsed time calculations: finding duration between times rounded to the nearest minute through these 5 detailed exercises.

Solution: Exercises 1 to 3
1 Basic Elapsed Time to the Minute
Exercise 1
The movie started at 2:15 PM and ended at 4:40 PM. How much time passed? Round to the nearest minute.
Definition:

Elapsed Time to the Nearest Minute: The amount of time that passes between a start time and an end time, calculated with precision to the minute.

Elapsed Time Method:
  1. Identify the start time and end time
  2. Count the hours from start to end
  3. Count the minutes from start to end
  4. Combine hours and minutes for the total
Step 1: Identify start and end times

Start time: 2:15 PM, End time: 4:40 PM

Step 2: Calculate hours

From 2:15 PM to 3:15 PM = 1 hour
From 3:15 PM to 4:15 PM = 1 hour
Total hours: 2 hours

Step 3: Calculate remaining minutes

From 4:15 PM to 4:40 PM = 25 minutes

Step 4: Combine hours and minutes

2 hours + 25 minutes = 2 hours 25 minutes

2 hours 25 minutes passed
Final answer:

2 hours 25 minutes passed between 2:15 PM and 4:40 PM.

Applied rules:

• Time Subtraction: End time - Start time = Elapsed time

• Hour Counting: Count full hours first

• Minute Counting: Count remaining minutes after hours

2 Elapsed Time with Borrowing
Exercise 2
The school play started at 10:30 AM and ended at 11:15 AM. How much time passed? Round to the nearest minute.
Definition:

Borrowing in Time: When the minutes in the start time are greater than the minutes in the end time, borrow 1 hour (60 minutes) from the hour column.

Step 1: Identify start and end times

Start time: 10:30 AM, End time: 11:15 AM

Step 2: Compare minutes

Start minutes (30) > End minutes (15), so we need to borrow

Step 3: Borrow 1 hour

Convert 11:15 AM to 10:75 AM (add 60 minutes to 15 minutes)

Step 4: Calculate minutes

From 10:30 AM to 10:75 AM = 45 minutes

Step 5: Calculate hours

Since we borrowed 1 hour and both times are in the same hour now, the hour difference is 0

45 minutes passed
Final answer:

45 minutes passed between 10:30 AM and 11:15 AM.

Applied rules:

• Borrowing Rule: When start minutes > end minutes, borrow 1 hour = 60 minutes

• Minute Subtraction: (End minutes + 60) - Start minutes

• Hour Adjustment: Reduce hour by 1 when borrowing

3 Crossing the Hour
Exercise 3
Lunch started at 11:45 AM and ended at 12:20 PM. How much time passed? Round to the nearest minute.
Definition:

Crossing the Hour: When calculating elapsed time that goes past the next hour, break the calculation into two parts: before the hour and after the hour.

Step 1: Identify the time periods

Before noon: 11:45 AM to 12:00 PM
After noon: 12:00 PM to 12:20 PM

Step 2: Calculate time before noon

From 11:45 AM to 12:00 PM = 15 minutes

Step 3: Calculate time after noon

From 12:00 PM to 12:20 PM = 20 minutes

Step 4: Add the two periods together

15 minutes + 20 minutes = 35 minutes

Lunch lasted 35 minutes
Final answer:

Lunch lasted 35 minutes from 11:45 AM to 12:20 PM.

Applied rules:

• Breaking at Hour: Split time calculations at the next hour mark

• Minute Calculation: Count minutes to the next hour, then minutes after

• Sequential Addition: Add separate time periods to get total elapsed time

Elapsed Time Rules and Methods
Elapsed Time = End Time - Start Time
Time Calculation Formula
Borrowing Rule
Start Min > End Min → Borrow 60
Adjust for minute subtraction
Time Subtraction
End - Start = Elapsed
Calculate duration
Crossing Hour
Split at Next Hour
Calculate in two parts
Key Definitions:

Start Time: The beginning time of an event

End Time: The finishing time of an event

Elapsed Time: The total amount of time that passes between start and end

Basic Rule: Subtract the start time from the end time to find elapsed time.
Borrowing: When start minutes > end minutes, borrow 1 hour (60 minutes).
Crossing Hours: Split calculations at the next hour mark for easier computation.
Tip 1: Use a number line to visualize time passing from start to end.
Tip 2: When crossing an hour, count minutes to the next hour first.
Tip 3: Remember that 60 minutes equals 1 hour when borrowing.
Solution: Exercises 4 to 5
4 Real-Life Application
Exercise 4
A soccer practice started at 3:45 PM and lasted for 1 hour and 35 minutes. What time did it end? Round to the nearest minute.
Definition:

Time Addition: Adding a duration to a start time to find the end time.

Step 1: Add the full hour to start time

3:45 PM + 1 hour = 4:45 PM

Step 2: Add the remaining minutes

4:45 PM + 35 minutes = 5:20 PM (since 45 + 35 = 80 minutes = 1 hour 20 minutes)

Step 3: Verify the calculation

Start: 3:45 PM, Duration: 1 hour 35 minutes, End: 5:20 PM

Step 4: Check the result

From 3:45 PM to 4:00 PM = 15 minutes
From 4:00 PM to 5:00 PM = 60 minutes
From 5:00 PM to 5:20 PM = 20 minutes
Total: 15 + 60 + 20 = 95 minutes = 1 hour 35 minutes ✓

Practice ended at 5:20 PM
Final answer:

The soccer practice ended at 5:20 PM.

Applied rules:

• Time Addition: Add hours and minutes separately

• Conversion: 60 minutes equals 1 hour

• Verification: Check by calculating elapsed time back

5 Complex Elapsed Time
Exercise 5
A movie marathon started at 1:35 PM and ended at 5:20 PM. During the marathon, there was a 15-minute break. What was the actual movie time (excluding the break)? Round to the nearest minute.
Definition:

Actual Time Calculation: Finding the active time by subtracting breaks from the total elapsed time.

Step 1: Calculate total elapsed time

From 1:35 PM to 2:00 PM = 25 minutes
From 2:00 PM to 3:00 PM = 60 minutes
From 3:00 PM to 4:00 PM = 60 minutes
From 4:00 PM to 5:00 PM = 60 minutes
From 5:00 PM to 5:20 PM = 20 minutes
Total: 25 + 60 + 60 + 60 + 20 = 225 minutes

Step 2: Convert to hours and minutes

225 minutes = 3 hours 45 minutes (since 225 ÷ 60 = 3 remainder 45)

Step 3: Subtract the break time

Actual movie time = Total time - Break time
Actual movie time = 3 hours 45 minutes - 15 minutes = 3 hours 30 minutes

Step 4: Convert to minutes for final answer

3 hours 30 minutes = (3 × 60) + 30 = 180 + 30 = 210 minutes

Actual movie time was 3 hours 30 minutes (210 minutes)
Final answer:

The actual movie time was 3 hours 30 minutes (210 minutes) excluding the 15-minute break.

Applied rules:

• Total Time Calculation: Calculate the full elapsed time first

• Break Subtraction: Subtract inactive time from total time

• Unit Conversion: Convert between hours and minutes as needed

Key Concepts: Elapsed Time to the Nearest Minute, Definitions, Methods, and Formulas
Elapsed Time = End Time - Start Time
Time Calculation Formula
Key definitions:

Elapsed Time: The amount of time that passes between a start time and an end time

Start Time: The time when an event begins

End Time: The time when an event finishes

Complete methodology:
  1. Identify times: Find the start and end times of the event
  2. Check minutes: If start minutes > end minutes, use borrowing method
  3. Calculate hours: Count the full hours between times
  4. Calculate minutes: Count the remaining minutes
  5. Add together: Combine hours and minutes for the total
Tip 1: Draw a timeline to visualize the passage of time.
Tip 2: When borrowing, remember to reduce the hour by 1 and add 60 to minutes.
Tip 3: Remember that 12:00 AM is midnight, and 12:00 PM is noon.
Tip 4: Check your answer by adding the elapsed time back to the start time.
Common errors: Forgetting to borrow when needed, incorrect minute calculations, adding instead of subtracting.
Exam preparation: Practice with various time combinations, work on borrowing skills, understand AM/PM differences.
Formulas to know by heart:

• Basic Formula: Elapsed Time = End Time - Start Time

• Borrowing Rule: When Start Minutes > End Minutes, borrow 1 hour = 60 minutes

• Time Addition: Start Time + Duration = End Time

• Unit Conversion: 60 minutes = 1 hour

Exercise with Visualization: Daily Activities
Exercise 6: Time Management
Daily schedule for a 3rd grader:
Math homework: 4:15 PM - 4:45 PM
Reading: 4:50 PM - 5:25 PM
Snack time: 5:30 PM - 5:45 PM
Free play: 5:50 PM - 6:20 PM
How much total time is spent on these activities?

Analysis: Calculate the time for each activity and add them together.

  • Math homework: 4:15 PM to 4:45 PM = 30 minutes
  • Reading: 4:50 PM to 5:25 PM = 35 minutes
  • Snack time: 5:30 PM to 5:45 PM = 15 minutes
  • Free play: 5:50 PM to 6:20 PM = 30 minutes
  • Total: 30 + 35 + 15 + 30 = 110 minutes = 1 hour 50 minutes

Questions & Answers

Question: My 3rd grade students struggle with borrowing when calculating elapsed time. How can I help them understand this concept?

Answer: Here are helpful strategies for teaching time borrowing:

  • Real-world analogy: Explain it like exchanging a dollar bill for 4 quarters when you need exact change
  • Time-specific analogy: "We can't subtract 45 minutes from 20 minutes, so we borrow 1 hour and turn it into 60 minutes"
  • Visual demonstration: Show how 1 hour = 60 minutes using analog clocks

Example: For 11:20 AM - 10:45 AM:

  • We can't do 20 - 45 minutes
  • Borrow 1 hour from 11, making it 10:80 AM
  • Now we can do 80 - 45 = 35 minutes
  • Hours: 10 - 10 = 0 hours
  • Total: 35 minutes

Practice with many examples where borrowing is needed until the concept becomes natural.

Question: My child gets confused when elapsed time crosses the hour. What strategies can help them?

Answer: Effective strategies for crossing the hour:

  • Break at the next hour: Always split the calculation at the next hour mark
  • Count to the next hour: First count minutes to reach the next hour
  • Then count beyond: Count minutes after reaching the next hour

Example: From 2:45 PM to 3:15 PM:

  • From 2:45 PM to 3:00 PM = 15 minutes
  • From 3:00 PM to 3:15 PM = 15 minutes
  • Total: 15 + 15 = 30 minutes

Practice with analog clocks to help visualize the minute hand moving past the 12.

Question: How do I know when I need to borrow? Sometimes I try to subtract and get a weird answer.

Answer: You need to borrow when the minutes in the start time are greater than the minutes in the end time. Here's how to recognize it:

  • Compare minutes only: Look at just the minutes part of both times
  • If start minutes > end minutes: You need to borrow
  • Example: 3:20 PM to 4:15 PM → 20 > 15? No, so no borrowing needed
  • Example: 2:45 PM to 3:30 PM → 45 > 30? Yes, so you need to borrow

When you borrow:

  • Take 1 hour from the hour column
  • Add 60 minutes to the minutes column
  • Now you can subtract normally

Always check: if your answer gives negative minutes, you forgot to borrow!

Question: What happens if I have to borrow but the hour is 12? Like going from 12:10 PM to 1:05 PM?

Answer: When borrowing from 12 o'clock, you still follow the same borrowing process, but the hour changes to 11:

For 12:10 PM to 1:05 PM:

  • Start: 12:10 PM, End: 1:05 PM
  • Compare minutes: 10 > 5? No, so no borrowing needed
  • Actually: From 12:10 PM to 1:00 PM = 50 minutes, then 1:00 PM to 1:05 PM = 5 minutes
  • Total: 50 + 5 = 55 minutes

But if you had 12:05 PM to 1:10 PM:

  • This doesn't require borrowing since 5 < 10
  • However, for 1:05 PM to 12:10 PM (going backwards), you'd cross midnight

The key is that when borrowing from 12, it becomes 11:70 (not 11:60) because you're borrowing from the previous hour in the sequence.

Question: How do I convert minutes to hours and minutes? Like if I get 95 minutes, how do I write it in hours and minutes?

Answer: To convert minutes to hours and minutes, divide by 60 and use the quotient and remainder:

  • Divide by 60: The whole number part is the hours
  • The remainder is minutes: What's left after dividing by 60

For 95 minutes:

  • 95 ÷ 60 = 1 remainder 35
  • So 95 minutes = 1 hour 35 minutes

More examples:

  • 120 minutes = 2 hours (120 ÷ 60 = 2 remainder 0)
  • 135 minutes = 2 hours 15 minutes (135 ÷ 60 = 2 remainder 15)
  • 180 minutes = 3 hours (180 ÷ 60 = 3 remainder 0)

You can also think: "How many groups of 60 minutes fit into my total?" That's your hours, and what's left over is your minutes.