Ticking Clocks and Turning Calendar — Class 4 Mathematics (CBSE)

From the current NCERT Maths Mela Grade 4 book, Chapter 12. Clocks tick through the day and calendars turn through the year — let us read them well.

1. Why this chapter matters

Time runs our day. Reading a clock and a calendar, knowing a.m./p.m., and finding how long things take helps children plan, be punctual, and manage their day.

2. Core ideas

Idea 1 — Units of time

60 seconds = 1 minute, 60 minutes = 1 hour, 24 hours = 1 day, 7 days = 1 week, 12 months = 1 year.

Method 2 — Read the clock

The short hand shows the hour; the long hand shows the minutes. Long hand on 12 = o'clock, on 6 = half past (:30), on 3 = quarter past (:15), on 9 = quarter to.

Skill 3 — a.m./p.m., calendar, and duration

a.m. is before noon, p.m. after noon. A calendar shows days, weeks, months, dates (and a leap year has 29 days in February). Duration is how long something lasts (end time − start time).

3. Worked examples

Example 1: The long hand is on 3 and the short hand just past 4. What time is it?

Quarter past 4 (4:15).

Example 2: How many days are in a week, and months in a year?

7 days and 12 months.

Example 3: A film starts at 4:00 and ends at 6:00. How long is it?

6:00 − 4:00 = 2 hours.

4. Activity corner

Make a paper clock and show half past 7, quarter past 5, and your school start time. Then circle today's date on a calendar and find the day one week later. Write:

• The times you showed
• Today's date and the date one week later
• The maths idea (reading clocks and calendars)

5. Common mistakes

• Mistake: Mixing up the hour and minute hands. Fix: Short hand = hour, long hand = minutes.
• Mistake: Confusing quarter past and quarter to. Fix: Quarter past is :15 (after the hour); quarter to is :45 (before the next hour).
• Mistake: Forgetting a.m. and p.m. Fix: a.m. is morning (before noon); p.m. is afternoon/evening (after noon).

6. How to write better answers

1. Read the hour from the short hand.
2. Read minutes from the long hand (o'clock, quarter, half).
3. Add a.m. or p.m. if needed.
4. For duration, subtract the start time from the end time.

7. Practice set

1. How many minutes are in one hour?
2. What time is quarter past 6?
3. What time is half past 9?
4. How many days are there in one week?
5. A class starts at 9:00 and ends at 11:00. How long is it?
6. Is 7 in the morning written as a.m. or p.m.?

8. Answer key

1. 60 minutes.
2. 6:15.
3. 9:30.
4. 7 days.
5. 2 hours.
6. a.m.

9. Quick revision

• 60 sec = 1 min; 60 min = 1 hr; 24 hr = 1 day; 7 days = 1 week; 12 months = 1 year.
• Short hand = hour; long hand = minutes.
• O'clock (:00), quarter past (:15), half past (:30), quarter to (:45).
• a.m. is before noon; p.m. is after noon.
• Duration = end time − start time.