Page 329 - Math Smart - 7

CHAPTER 15.1

In this chapter

Time • know the relationships
Pupils should be able to:
between units of time
15.1.1 Reading and writing time in • understand and use
12-hour and 24-hour
the 24-hour notation clock systems
• interpret timetables
Let us recall telling time using the 24-hour notation. We can draw a diagram to • calculate time intervals
show the time line in one day. There are 12 hours from midnight to noon, and
12 hours from noon to midnight. This makes up 24 hours in one day.

midnight
midnight noon
12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 10 11 12
—I 1 1 1 \ 1 1 1 1 i 1 1 1 1 1 1 1 1 1 i 1 -I-
00 00 01 00 02 00 03 00 04 00 05 00 0600 07 00 08 00 09 00 10 00 11 00 12 CO 13 00 14 00 15 00 1600 17 00 18 00 19 00 20 00 21 00 22 00 23 00 00 00

We can see that
• 9.00 a.m. is written as 09 00, and
• 5.00 p.m. is written as 17 00.

When we write time
using the 24-hour clock
Write the time using the 24-hour notation. notation, we do not
a) 3.15 a.m. b) 10.47 a.m. c) 1.30 p.m. d) 9.24 p.m. need to write 'a.m.' or
'p.m.'. Instead, the time
Solution
is written using four
a) We write 3.15 a.m. in the 24-hour notation as 03 15. digits. The first two digits
b) We write 10.47 a.m. in the 24-hour notation as 10 47. represent the hours
c) We write 1.30 p.m. in the 24-hour notation as 13 30. and the last two digits
represent the minutes.
d) We write 9.24 p.m. in the 24-hour notation as 21 24.

0000 03 15 1047 1200 1330 21 24 00 00

^ RECALL

O Mandy woke up later than usual at 6.15 for work this morning. She usually woke up 45 min earlier.
At what time did she usually wake up for work?
@ Anthony went on a vacation to Vietnam from 12 September to 21 September. How long did his
vacation last in weeks and days?
O Express each of the following times in 24-hour clock notation.
a) 4.08 a.m. b) 10.25 a.m. c) 11.12 p.m.
O Express each of the following times in 12-hour clock notation. Write the times using a.m. or p.m.
a) 00 45 b) 09 48 c) 16 39
Q Mr Sanchez took a flight from Singapore to London. The duration of the flight was 13 h 35 min.
If he arrived in London at 05 50 the next day, at what time did Mr Sanchez leave Singapore?
Express your answers in 12-hour clock notation.