Year 4 Maths: The 24-hour Clock

Introduction to the 24-hour Clock

Hello Year 4! Today, we are going to learn about the 24-hour clock. This clock is different from the clock you might see on your wall or in your home, which is called the 12-hour clock.

What is the 24-hour Clock?

The 24-hour clock runs from 00:00 (which is midnight) to 23:59 (which is one minute before midnight the next day). In this system, the hours are counted from 0 to 23 instead of 1 to 12.

How Does It Work?

Here’s how the 24-hour clock works:

• Midnight (12:00 AM) is written as 00:00.
• 1:00 AM becomes 01:00.
• 2:00 AM becomes 02:00.
• This continues until 11:00 AM, which is 11:00.
• Then, at 12:00 PM (noon), it becomes 12:00.
• After noon, we continue counting:
  • 1:00 PM becomes 13:00.
  • 2:00 PM becomes 14:00.
  • And it goes on until 11:00 PM, which is 23:00.

Quick Summary of Key Rules

1. Midnight is 00:00.
2. Noon is 12:00.
3. For times after 12:00 PM, add 12 to the hour.
   • Example: 1:00 PM is 1 + 12 = 13:00.
4. The minutes stay the same.

Tips and Tricks

• Remember: If it’s morning (before noon), just add a zero in front of the hour (for 1:00 AM to 9:00 AM).
• Use a number line: Visualise the hours from 0 to 23 on a number line to see how they relate.
• Practice: Convert times from 12-hour to 24-hour and vice versa as much as you can!

Practice Questions

Now that we understand the 24-hour clock, let’s try some practice questions!

Easy Level Questions

1. What is 00:00 in the 12-hour clock?
2. What is 12:00 in the 24-hour clock?
3. What is 10:00 AM in the 24-hour clock?
4. What is 3:00 PM in the 24-hour clock?
5. Convert 9:00 AM to the 24-hour clock.
6. Convert 1:00 PM to the 24-hour clock.
7. What time is 15:00 in the 12-hour clock?
8. What time is 18:00 in the 12-hour clock?
9. What is 22:00 in the 12-hour clock?
10. What is 11:00 PM in the 24-hour clock?

Medium Level Questions

11. Convert 12:30 AM to the 24-hour clock.
12. Convert 5:45 PM to the 24-hour clock.
13. What is 14:15 in the 12-hour clock?
14. What is 16:30 in the 12-hour clock?
15. Convert 7:00 PM to the 24-hour clock.
16. What is 00:30 in the 12-hour clock?
17. If it is 21:00, what time is it in the 12-hour clock?
18. What is 13:59 in the 12-hour clock?
19. If you wake up at 06:00, what time is it in the 12-hour clock?
20. What time is 19:45 in the 12-hour clock?

Hard Level Questions

21. If school starts at 08:45, what time is that in the 12-hour clock?
22. If a movie starts at 18:15, what time is that in the 12-hour clock?
23. If it is 02:30 AM, what is it in 24-hour time?
24. What is the time 3 hours after 14:00?
25. What is the time 4 hours before 23:00?
26. Convert 11:59 PM to the 24-hour clock.
27. If you have a meeting at 17:30, what time is that in the 12-hour clock?
28. What is the time 1 hour before 22:00?
29. If you finish school at 15:20, what time is that in the 12-hour clock?
30. Convert 09:15 PM to the 24-hour clock.

Answers with Explanations

Easy Level Answers

1. 00:00 → Midnight
2. 12:00 → Noon
3. 10:00 AM → 10:00
4. 3:00 PM → 15:00
5. 9:00 AM → 09:00
6. 1:00 PM → 13:00
7. 15:00 → 3:00 PM
8. 18:00 → 6:00 PM
9. 22:00 → 10:00 PM
10. 11:00 PM → 23:00

Medium Level Answers

11. 12:30 AM → 00:30
12. 5:45 PM → 17:45
13. 14:15 → 2:15 PM
14. 16:30 → 4:30 PM
15. 7:00 PM → 19:00
16. 00:30 → 12:30 AM
17. 21:00 → 9:00 PM
18. 13:59 → 1:59 PM
19. 06:00 → 6:00 AM
20. 19:45 → 7:45 PM

Hard Level Answers

21. 08:45 → 8:45 AM
22. 18:15 → 6:15 PM
23. 02:30 AM → 02:30
24. 17:00 (which is 5:00 PM)
25. 19:00 (which is 7:00 PM)
26. 11:59 PM → 23:59
27. 17:30 → 5:30 PM
28. 21:00 → 9:00 PM
29. 15:20 → 3:20 PM
30. 09:15 PM → 21:15

Great job, everyone! Keep practicing the 24-hour clock, and you will become a pro in no time!