Time does not work in tens and hundreds like metres or money. Learn the facts: 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day and 7 days in a week. To change to a smaller unit, multiply: 3 hours = 3 × 60 = 180 minutes. To change to a bigger unit, divide. With mixed units, change the big unit first, then add the extra part. Be careful with decimals: 1.5 hours means one and a half hours, which is 90 minutes, not 1 hour 50 minutes.
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Move the hands
3:00
The short hand moves between hour numbers as the minutes pass. One full turn of the long hand is sixty minutes.
Words to know
- convert
- change a measurement into a different unit
- minute
- a unit of time; there are 60 in an hour
- decimal hour
- part of an hour written as a decimal, like 0.5 for half an hour
Worked examples
How many minutes are in 4 hours?
- 1.There are 60 minutes in 1 hour.
- 2.4 × 60 = 240.
= 240
How many minutes are in 2 hours 15 minutes?
- 1.2 hours = 2 × 60 = 120 minutes.
- 2.120 + 15 = 135.
= 135
How many minutes are in 1.5 hours?
- 1.1.5 hours is 1 hour and half an hour.
- 2.60 + 30 = 90. It is not 1 hour 50 minutes.
= 90
For parents
Method: Use the time facts: 60, 60, 24, 7
What to say: Which fact do we need here, 60, 24 or 7? Should the number get bigger or smaller?
Common mistakes:
- Treats time as if it worked in tens and hundreds, like money or metres (1 hour = 100 minutes, 2 h 15 min = 215 minutes).
- Reads the digits after a decimal point as minutes (1.5 hours = 1 h 50 min), or writes hours and minutes as a decimal (1 h 30 min = 1.30 h).
- Uses the wrong conversion fact: 24 for minutes in an hour, or 60 for hours in a day.
- Thinks a day has 12 hours, because the clock face only shows 12.
- Converts only the whole units and leaves out the extra part (the minutes after the hours, or the part of an hour).
- Multiplies when changing to a bigger unit, so the answer gets bigger instead of smaller.