Elapsed time is how long passes between a start time and a finish time. Because an hour has 60 minutes, not 100, you cannot just subtract the digits. Count up in two hops instead: first to the next o'clock, then on to the finish. From 3:50 to 4:10, it is 10 minutes up to 4:00 and 10 minutes more to 4:10, which is 20 minutes altogether. When the minutes seem to go backwards, it is a sign the hour has rolled over.
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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
- elapsed time
- the amount of time between a start and a finish
- o'clock
- a time with zero minutes, like 4:00
- minute
- a unit of time; there are 60 in an hour
Worked examples
3:50 to 4:10
- 1.3:50 to 4:00 is 10 min.
- 2.4:00 to 4:10 is 10 min. Total 20 min.
= 20
2:40 to 3:15
- 1.2:40 to 3:00 is 20 min.
- 2.3:00 to 3:15 is 15 min. Total 35 min.
= 35
6:35 to 7:05
- 1.6:35 to 7:00 is 25 min.
- 2.7:00 to 7:05 is 5 min. Total 30 min.
= 30
For parents
Method: Count up on a clock face in two hops.
What to say: Say 'how many minutes to the next o'clock, then how many more?' rather than subtracting the digits.
Common mistakes:
- Subtracting the readings as if an hour had 100 minutes.
- Stopping at the next o'clock and forgetting the minutes past it.