Between two times, even across midnight
Convert times into minutes and check the day before finding elapsed time.
Begin with the activity ↓From 9:45 to 10:20: is that seventy-five minutes?
Hours are groups of sixty minutes. Check whether the endpoint is on the same or next day, then count the minutes between.
Reading starts at 9:45 and ends at 10:20. There are fifteen minutes to 10:00 and twenty more after it, making thirty-five. Do not subtract these clock times as decimal numbers.
You can also count minutes since midnight. The first time is 9×60+45=585 minutes and the second is 620. Subtract matching units to get thirty-five minutes.
Start at 23:50 and finish at 00:15 the next day. Ten minutes reach midnight and fifteen more follow, giving twenty-five. The phrase next day is essential.
In minute counts, add 24×60=1440 for the next day. The endpoint is 1440+15 and the start is 1430, so the difference is twenty-five.
Do not automatically assume a smaller clock reading is on the next day. On the same day, an endpoint of 9:45 precedes a start of 10:20. Check the date or correct the input.
Equal clock readings can still give different durations. From 9:00 to 9:00 on the same day is zero minutes; to 9:00 the next day is 1440 minutes. Read the conditions before calculating.
Listen one paragraph at a time
Hold on to this distinction
If the endpoint looks earlier, ask about the day. Use sixty-minute hours and one common minute unit.
Change it and check
Choose start and end times and whether the end is on the same or next day. See how changing only the day affects the result.
620 − 585 = 35 minutes
0 hours and 35 minutes elapsed.
Check the day first and convert hours to sixty-minute groups. The same clock reading on the next day adds a day.
These exercises use the same time zone and a 24-hour day without clock adjustments. Real travel across time zones or daylight-saving changes is outside this activity.
Try with paper and objects
Write 23:50 → midnight → next-day 00:15 on paper and label the gaps ten and fifteen minutes. Mark the day boundary.
Check and explain another example
Check your idea 1
Check your idea 2
Apply it in a new setting
Connect the answer to its unit
Return to the explanationCompare with a solution
75 · minutes
Five plus sixty plus ten gives seventy-five minutes.
Does your explanation include these ideas?
Explain aloud or in a drawing, then check your ideas. Different wording can express the same meaning.
Continue, or pause here
Use scale intervals and rounding conventions to distinguish exact values from approximations.