Time and Unit Conversion
Time is measured with clocks and calendars. Accurate conversion between units helps us solve duration, timetable and travel problems.
Units of time
The basic relationships are 60 seconds = 1 minute, 60 minutes = 1 hour, 24 hours = 1 day, 7 days = 1 week, 12 months = 1 year, 10 years = 1 decade and 100 years = 1 century. A common year has 365 days; a leap year has 366 days.
Reading a clock
The short hand shows hours and the long hand shows minutes. Read the minutes first, then the hour. For a 24-hour time, afternoon times from 1 p.m. to 11 p.m. are written by adding 12 to the hour.
Worked examples
- 120 seconds ÷ 60 = 2 minutes.
- 180 minutes ÷ 60 = 3 hours.
- If a journey lasts 45 minutes and arrival is at 8:00 a.m., departure is 7:15 a.m.
Practice
- Convert 5 minutes to seconds and 2.5 hours to minutes.
- How many hours and minutes are there from 07:30 to 15:00?
- A bus leaves at 09:45 and travels for 2 hours 35 minutes. Find its arrival time.
