Grade 4 · Unit 5: Using units of measurement

The 24-hour clock

From 00:00 to 23:59.

Airports use the 24-hour clock.

Flight times

An airport screen says the flight leaves at 17:45. This is the 24-hour clock. 17:45 is 5:45 p.m.

12-hour and 24-hour

Morning times stay the same (with a 0 in front). Afternoon: add 12. 3 p.m. → 15:00. Midnight is 00:00.

Working out durations

Count to the next hour: 09:45 → 10:00 is 15 minutes. Then whole hours: 10:00 → 13:00 is 3 hours. Then minutes: 13:00 → 13:30 is 30 minutes. Total: 3 h 45 min.

Timetables

Bus 1 takes 5 h 30 min from Dhaka to Chattogram. Bus 3 travels overnight – past midnight! Which bus is fastest?

Time zones

When it is afternoon in Dhaka, it is morning in London. Places east of us are ahead; places west are behind. Compare times carefully: quarter to four (15:45) is later than 15:40.

What I learnt