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1Reading the Clock2AM, PM & the Calendar3Calendar Day-Arithmetic4Elapsed Time5Indian Money6Money from a Picture7Money Word Problems

Concept 4 of 7

Elapsed Time: How Long Did It Take?

1

Today's big idea

Hopping from the start time to the next whole hour beats subtracting hours and minutes.

Minutes stop at 60, not 100, so column subtraction is the wrong tool here.

2

How it works

👀 What's going on?

Minutes are not like ordinary numbers. Sixty of them make an hour, not a hundred. So stacking 4:15 over 2:30 and subtracting in columns goes wrong fast.

💡 Here's the trick

Elapsed time — jump method2:303:004:004:1530 min1 hour15 minTotal = 1 h 45 minJump to the next hour, then to the end. Add the jumps.

Look at the number line above. Instead of subtracting, it walks from 2:30 to 4:15 in three easy hops. First 30 minutes up to 3:00, then a whole hour to 4:00, then the last 15 minutes. Add the hops and you get 1 hour 45 minutes.

🪄 How to do it

  1. 1.Mark the start time and the end time on a line, like the number line above.
  2. 2.Hop to the next whole hour, then hop in whole hours as far as you can.
  3. 3.Hop the last few minutes to the end, then add every hop together.

✍️ Try it

Cricket practice runs from 7:40 AM to 9:10 AM. How long is it? Now a harder one. A car leaves at 11:45 AM and arrives at 1:20 PM. How long is the drive?

Practice: 7:40 to 8:00 is 20 minutes, 8:00 to 9:00 is 1 hour, 9:00 to 9:10 is 10 minutes. Total = 1 hour 30 minutes. Drive: 11:45 to 12 noon is 15 minutes, 12 noon to 1:00 PM is 1 hour, then 20 minutes more. Total = 1 hour 35 minutes.

⚠️ Watch out

You might be thinking 11:45 AM to 1:20 PM is nearly 2 hours, because 1 comes long after 11. Hop it instead. The clock resets to 12 at noon, so the real gap is only 1 hour 35 minutes.

🌟 Why this matters

You use elapsed time every single day. How long is the journey? When does the cake come out of the oven? Can you finish one more game before dinner? Slip by an hour and you miss the train. Hopping to the next whole hour keeps you safe, because you never have to borrow across 60.
Exam tip: Watch for a start in the morning and an end in the afternoon, and hop through 12 noon rather than past it.

3

Watch me solve one

Quanta solves it

“Watch how I think through one of these — then you try.”

THE PROBLEM

“A bus leaves at 9:25 AM and reaches at 11:10 AM. How long is the journey?”

  1. 1

    Jump to the next full hour

    9:25 → 10:00 = 35 minutes. ⏱️

  2. 2

    Jump full hours

    10:00 → 11:00 = 1 hour.

  3. 3

    Jump to the end

    11:00 → 11:10 = 10 minutes.

  4. 4

    Add all jumps ✓

    35 + 60 + 10 = 1 hour 45 minutes

Now you try one — same steps, different story 👇

4

See it in action

⚡ Time to play!

Hop from 2:00 to 5:00. How long is that?

ELAPSED TIME · ROUND 1 OF 3

START

2:00

NOW

2:00

END

5:00

Elapsed: 0 min
5

Quick check

✅ VERIFICATION

A film is 2 hours 20 minutes long and starts at 6:50 PM. What time does it end?

⚡ Finish the activity above first to answer.

Keep going!

Up next: Indian Money

Sort, multiply, then add, find any money total.

Concept 5 of 7 →