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NCERT Solutions for Class 5th Maths Chapter 12 hour format and 24-hour format — Let us find out (continued)

Book page 15612 Updated on2026-09-19

Q6.
Fill in the blanks by writing the time in the appropriate format. 05:30 a.m. — 05:30 hours; ………… — 08:35 hours; 11:55 a.m. — ……… hours; 02:30 p.m. — 14:30 hours; 05:30 p.m. — ……… hours; 09:35 p.m. — ……… hours.
Answer

Here is the completed table. The two filled rows the book gives us show exactly what to do.

Time in 12-hour formatTime in 24-hour format
05:30 a.m.05:30 hours
08:35 a.m.08:35 hours
11:55 a.m.11:55 hours
02:30 p.m.14:30 hours
05:30 p.m.17:30 hours
09:35 p.m.21:35 hours

The rule, in two lines:

  1. a.m. time → write the same numbers, just say hours instead of a.m. Nothing changes.
  2. p.m. time → add 12 to the hour. The minutes never change.
08:35 hours is before 12, so it is morning → 08:35 a.m.
11:55 a.m. is morning → 11:55 hours
05:30 p.m. → 5 + 12 = 17 → 17:30 hours
09:35 p.m. → 9 + 12 = 21 → 21:35 hours
Why we add 12: A full day is 24 hours long, but a clock face has only 12 numbers. So the same 12 numbers get used twice in a day. The 24-hour way does not reuse them — it keeps counting: after 12 noon comes 13, 14, 15 and so on up to 23. Every p.m. hour is 12 hours after its a.m. twin, so we add 12.
Where you have seen this: Look at a railway ticket or the board at a bus stand. A train at 17:30 hours is a train at 5:30 in the evening. Nobody has to ask whether it is morning or evening — that is the whole point of the 24-hour format.
Q7.
Match the following. Time in 12-hour format: 06:30 a.m., 08:45 p.m., 11:45 p.m., 04:30 a.m., 07:30 p.m., 01:30 a.m. Time in 24-hour format: 01:30 hours, 23:45 hours, 06:30 hours, 20:45 hours, 04:30 hours, 19:30 hours.
Answer

Here are the six correct pairs.

12-hour formatWorking24-hour format
06:30 a.m.morning, so no change06:30 hours
08:45 p.m.8 + 12 = 2020:45 hours
11:45 p.m.11 + 12 = 2323:45 hours
04:30 a.m.morning, so no change04:30 hours
07:30 p.m.7 + 12 = 1919:30 hours
01:30 a.m.after midnight, so no change01:30 hours

A quick way to match without any working:

  1. Every a.m. time matches the 24-hour time with the same digits. Spot those first: 06:30, 04:30 and 01:30.
  2. The three left over must be the p.m. ones. Their 24-hour hours are all bigger than 12: 20, 23 and 19.
  3. Match each by subtracting 12: 20 − 12 = 8, so 20:45 goes with 08:45 p.m. 23 − 12 = 11, so 23:45 goes with 11:45 p.m. 19 − 12 = 7, so 19:30 goes with 07:30 p.m.
Careful with 01:30 a.m.: This is half past one at night, just after midnight — not in the afternoon. In the 24-hour format it stays 01:30 hours. Midnight itself is written 00:00 hours.
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