Problem Set 44 – Seconds, am/pm and the 24-hour ClockClass 5 Maths · Chapter 10 Measuring Time · Problem Set 44 – Maharashtra Board

Summary: Problem Set 44 – Seconds, am/pm and the 24-hour Clock

The thin, fast hand is the second hand. The dial has 60 small parts; one part takes 1 second, a full round takes 60 seconds = 1 minute.

A new day starts at 12 midnight. Times from midnight to 12 noon are am (ante meridiem); times from noon to midnight are pm (post meridiem). This is the 12-hour clock.

In the 24-hour clock the hours after noon keep counting: 1 pm = 13:00, 3:20 pm = 15:20, 11:50 pm = 23:50.

Morning times keep their number (with two digits): 7:45 am = 07:45. Midnight is 00:00, so 12:30 at night = 00:30; noon stays 12:00.

Trains, buses and planes use the 24-hour clock so nobody mixes up morning and evening.

Key points to remember

• 1 minute = 60 seconds
• am = from midnight to noon
• pm = from noon to midnight
• pm → 24-hour: add 12 to the hour (1 pm to 11 pm)
• am → 24-hour: same hour, two digits (07:45)
• 12 noon = 12:00; 12 midnight = 00:00
• 24-hour → pm: subtract 12 when the hour is 13 or more
• 6 am to 8 pm = 14 hours

Problem Set 44 – Seconds, am/pm and the 24-hour Clock – Notes

1. Seconds

• The second hand is long and thin and moves quickly.
• The clock face has 60 small marks. Moving one mark takes 1 second; one full round takes 60 seconds.
• In that full round the minute hand moves one small mark. So 1 minute = 60 seconds.
• We use seconds for races, counting heartbeats and reading a thermometer.

2. Changing minutes and seconds

• 3 minutes = 3 × 60 = 180 seconds.
• 2 minutes 15 seconds = 120 + 15 = 135 seconds.
• 150 seconds = 120 + 30 = 2 minutes 30 seconds.

3. am and pm

• The day begins at 12 midnight. After that come 1, 2, 3 … up to 12 noon — these are am times.
• After noon we count 1, 2, 3 … again up to 12 midnight — these are pm times.
• Working from 6 am to 8 pm: 6 am → 12 noon = 6 h, 12 noon → 8 pm = 8 h, so 14 hours, not 2!

4. The 24-hour clock

• Hours are counted from 0 to 23, with no am or pm. Digital timetables show just numbers like 18:20.
• For pm times from 1 pm to 11 pm, add 12 to the hour: 6:20 pm → 18:20.
• For am times, keep the hour: 6:20 am → 06:20. Just after midnight, 12 becomes 00: 12:05 am → 00:05.
• After 23:59 the clock shows 00:00 — midnight, and a new day.

5. Back to the 12-hour clock

• If the hour is 13 to 23, subtract 12 and write pm: 19:35 → 7:35 pm.
• If the hour is 01 to 11, write am: 08:10 → 8:10 am.
• 12:xx is just after noon (pm); 00:xx is just after midnight (am): 00:40 → 12:40 am.

Formulas at a glance

Key terms

Problem Set 44 – Seconds, am/pm and the 24-hour Clock – Flashcards

Read the question, answer it in your head, then tap the card to check. 10 cards.

Problem Set 44 – Seconds, am/pm and the 24-hour Clock – MCQ Quiz

10 questions. Tap an option — you will see at once if it is right and why.

How to study Problem Set 44 – Seconds, am/pm and the 24-hour Clock

⏱ About 25 minutes

1. Learn (5 min)
   Learn 1 minute = 60 seconds and what am and pm mean.
2. Convert (15 min)
   Change 12-hour times to 24-hour times and back (add or take away 12).
3. Practise (5 min)
   Do the 4 'Try it yourself' sums, take the quiz and play 🎮 Play.