Cambridge International Mathematics

28 Assumed Knowledge (Number)

9 Calculate the time:

a 3 hours after 8 : 16 am b 3 hours before 11 : 45 am

c 512 hours after 10 : 15 am d 312 hours before 1 : 18 pm

10 Boris caught a plane flight at 8 : 45 am. The flight was

612 hours. At what time did he arrive at his destination,

assuming it was in the same time zone?

11 If a train is travelling at 36 m/s, how far will it travel in

1 hour? Give your answer in kilometres.

24-HOUR TIME

In 24 -hour time, four digits are always used. For example:

² 0800 is 8 : 00 am

“Oh eight hundred hours”

² 2000 is 8 : 00 pm

“twenty hundred hours”

² 0000 is midnight ² 1200 is noon or midday

² 2359 is one minute before midnight

Morning times (am) are from midnight ( 0000 ) to midday ( 1200 ).

Afternoon times (pm) are from midday ( 1200 ) to midnight ( 0000 ).

Notice that: ² midnight is 0000 not 2400

² to convert afternoon 24 -hour time to pm times we subtract 1200.

1 Change to 24 -hour time:

a 9 : 57 am b 11 : 06 am c 4 o’clock pm

d 2 : 25 pm e 8 o’clock am f 1 : 06 am

g 8 : 58 pm h noon i 2 minutes past midnight

2 Change to am/pm time:

a 1140 b 0346 c 1634 d 1900

e 0800 f 2330 g 1223 h 2040

Departure Travelling time Arrival

a 0520 6 h 20 min

b 0710 1405

c 56 min 1027

d 4 h 23 min 1652

e 2012 0447 (next day)

3 Copy and complete the following railway

schedule:

EXERCISE I.2

24-hour time

am pm

is used by the armed forces and in train and airline timetables. It avoids the need for using

and to indicate morning and afternoon.

IGCSE01

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