One lap of the minute hand
A clock has two hands. The long hand is the minute hand, and the short hand is the hour hand. Around the face there are 60 small marks, and the minute hand moves from one mark to the next in one minute.
When the minute hand goes all the way round, from the 12 back to the 12, it passes all 60 marks, so 60 minutes have gone by. In that time the hour hand moves from one number to the next: one hour. So one hour is 60 minutes.
At 3:00 the minute hand points to the 12. The small marks around the face count the minutes, and there are 60 of them.
From 3:00 to 4:00 the minute hand goes once around the face: one hour, which is 60 minutes.
3:00 = 3 o'clock: the long hand is on 12 and the short hand points straight at 3
Set the clock to 4:00
Turning the minute hand once around, past all 60 marks, carries the hour hand from 3 to 4.
Writing h and min
Hour is shortened to h, and minute is shortened to min. So 1 hour = 60 minutes is written 1 h = 60 min.
Each hour holds 60 minutes, so 2 hours hold 60 + 60 = 120 minutes: 2 h = 120 min. An hour is not 100 minutes, so 2 h is not 200 min.
Half an hour
Half an hour is half of 60 minutes, which is 30 minutes. From 3:00 to 3:30 the minute hand goes from the 12 to the 6, half of the way around the face. So half an hour is 30 min.
At 3:30 the minute hand points to the 6. It has passed 30 of the 60 marks, half of the way around.
From 3:00 to 3:30 is half an hour, 30 minutes.
Minutes into hours and minutes
To change minutes into hours and minutes, take out groups of 60. For 150 minutes: 60 + 60 = 120 minutes make 2 hours, and 150 − 120 = 30 minutes are left over. So 150 min = 2 h 30 min.
The minutes part is always less than 60, because 60 more minutes would make another hour. To go back, change each hour into 60 minutes and add the rest: 2 h 30 min = 60 + 60 + 30 = 150 min.
Counting minutes along the line: two hops of 60 minutes are 2 hours, and 30 minutes more reach 150.
Worked example: Minutes Changed to Hours and Minutes, and Back Again
Question A film lasts 165 minutes. After the film, Hana's bus ride home takes 1 h 20 min. (a) How long is the film in hours and minutes? (b) How long is the bus ride in minutes?
1.1 hour is 60 minutes. Take groups of 60 minutes out of 165: 60 + 60 = 120. A third group would make 180, which is too many.
Two groups of 60 minutes fit in 165 minutes: 60 + 60 = 120. A third group would make 180. 2.2 hours use 120 minutes. The minutes left are 165 − 120 = 45.
2 hours use 120 minutes, and 165 − 120 = 45 minutes are left. 3.(a) The film lasts 2 h 45 min.
(a) The film lasts 2 h 45 min. 4.For the bus ride, change the 1 hour to 60 minutes and add the other 20 minutes: 60 + 20 = 80.
The 1 hour of the bus ride is 60 minutes: 60 + 20 = 80. 5.(b) The bus ride takes 80 minutes.
(b) The bus ride takes 80 minutes.
Answer: (a) 2 h 45 min; (b) 80 minutes
Common mistakes
- Writing 165 minutes as 1 h 65 min. The minutes part must be less than 60, because 60 of those minutes make another hour.
- Treating 1 hour as 100 minutes and writing 1 h 20 min as 120 minutes. An hour is 60 minutes, so 1 h 20 min is 60 + 20 = 80 minutes.
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