Grade 4 › G4U11 Time: Duration

Grade 4 › G4U11 Time: Duration › L2
GRADE 4 · ALBERTAOUTCOME AB-G4-4T1

L2 · Determining Duration: Start Time to End Time

Learning goal

“I can find how long an event lasts by counting on a timeline from the start time to the end time - jumping to the next hour first, then adding whole hours, then the leftover minutes - and I can give the duration in minutes or in hours and minutes.”

Duration — how long an event lasts, from its start to its end.
Start time — the time an event begins.
End time — the time an event finishes.
Timeline — a number line for time. We draw the start and end as marks and count the jumps between them.
Worked example

A puzzle club starts at 3:40 and ends at 4:15. How long does it last? Step 1: Draw a timeline. Mark the start, 3:40, and the end, 4:15. Step 2: Jump from 3:40 to the next whole hour, 4:00. That jump is 20 minutes (40 + 20 = 60, the top of the hour). Step 3: Jump from 4:00 to 4:15. That jump is 15 minutes. Step 4: Add the jumps: 20 + 15 = 35 minutes. The club lasts 35 minutes. Clock check: on a clock face, the minute hand travels from the 8 (40 minutes) past the top and on to the 3 (15 minutes) - a bit more than half a turn, which matches 35 of 60 minutes. Say it plainly: never count minute by minute. Jump to the next hour first - the first jump is always "60 minus the start minutes."

Check yourself — explain it

Why is the first jump from 3:40 equal to 20 minutes and not 40?

Paired problem — example still visible

A drawing class starts at 5:25 and ends at 5:50. How long is it? -> 25 minutes (one jump inside the hour: 50 - 25 = 25)

Faded completion — last step is yours

"A walk starts at 6:45 and ends at 7:10. First jump: 6:45 -> 7:00 = 15 minutes. Second jump: 7:00 -> 7:10 = 10 minutes. Total duration: 15 + 10 = ___ minutes." -> 25 minutes

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