Page 128 - Math Skill - 4

126 Maths

For example,
8 a.m. is written as 0800 hours. 11 12 1 Absorbing Facts

1 a.m. is written as 0100 hours. 10 22 23 24 13 14 2 The first invention of clock was
12 noon is written as 1200 hours. 9 21 15 3 the pendulum clock, which was
20 16
2 p.m. is written as 1400 hours. 8 19 18 17 4 designed and built by Dutch
11.30 p.m. is written as 2330 hours. 7 6 5 polymath christiaan huygens
in 1656.

12 mid-night is written as 2400 hours or 0000 hours.
Look at these clocks:
(a) (b) (c)
11 12 1 11 12 1 11 12 1
10 23 24 13 2 10 23 24 13 2 10 23 24 13 2
22 14 22 14 22 14
9 21 15 3 9 21 15 3 9 21 15 3
20 16 20 16 20 16
8 19 18 17 4 8 19 18 17 4 8 19 18 17 4
7 6 5 7 6 5 7 6 5

If it is in the morning, If it is in the morning
we say ‘the time is we say ‘the time is If it is in the morning,
we say ‘the time is
0230 hours’. 0610 hours’. 1107 hours’.

If it is in the afternoon, If it is in the evening, If it is at night, we say
we say, ‘the time is we say ‘the time ‘the time is 2307 hours’.
1430 hours’. 1810 hours’.

Conversion from 24-hour Clock to 12-hour Clock Time
Rule 1: If the number formed by the first two digits from the left is less than 12, it denotes the
number of hours belongs to before noon and thus a.m. is to be used with it.

For example, 0710 hours denotes 7:10 a.m and 1105 hours denotes 11:05 a.m.
Rule 2: If the number formed by the first two digits from the left is greater than 12, the difference
between the number and 12 gives the number of hours after noon and thus p.m. is to
be used with it.
For example, 1315 hours denotes 1:15 p.m. and 2230 hours denotes 10:30 p.m.

Rule 3: If the number formed by the first two digits from the left is 12 (other than 12:00), it
shows time after noon and so p.m. is to be used with it.
For example, 1205 hours denotes 12:05 p.m. and 1240 hours denotes 12:40 p.m.

Let’s Attempt

Example 1: Convert the following time into 24-hour clock time.
(a) 12:15 p.m. (b) 11:47 p.m. (c) 3:39 a.m.
Solution: (a) 12:15 p.m. = 1215 hours (b) 11:47 p.m. = 2347 hours
(c) 3:39 a.m. = 0339 hours