Grade 4 › G4U11 Time: Duration

Grade 4 › G4U11 Time: Duration › L4
GRADE 4 · ALBERTAOUTCOME AB-G4-4T1

L4 · Duration Problem Solving

Learning goal

“I can solve real duration problems in any direction: find the duration from the start and end, find the end time from the start and the duration, find the start time from the end and the duration, add durations together, and compare durations that wear different name tags.”

Schedule — a plan that lists events with their start times, end times, or durations.
Total duration — durations of two or more events added together into one length of time.
Compare — to say which of two durations is longer, and by how much, after both wear the same unit.
Time left — the duration still remaining until an event ends or begins.
Worked example

A swimming lesson lasts 40 minutes. Part 1 (find the end): the lesson starts at 4:25. Count ON 40 minutes on the timeline: 4:25 -> 5:00 is 35 minutes, then 5 more minutes lands at 5:05. The lesson ends at 5:05. Part 2 (find the start): a different lesson ends at 5:05 and lasts 40 minutes. Count BACK 40 minutes: 5:05 -> 5:00 is 5 minutes back, then 35 more minutes back lands at 4:25. The lesson started at 4:25. Clock check: both answers agree with L2 - from 4:25 to 5:05 the minute hand travels 35 + 5 = 40 minutes. Say it plainly: start, duration and end are three corners of one triangle. Given any two, the timeline finds the third - forward for an end, backward for a start, jumps between for a duration.

Check yourself — explain it

A show ends at 6:15 and lasts 30 minutes. To find the start time, we count back 30 minutes from 6:15 because...

Paired problem — example still visible

A craft class starts at 2:10 and lasts 35 minutes. What time does it end? -> 2:45 (2:10 -> 2:45 stays inside the hour)

Faded completion — last step is yours

"A movie ends at 8:20 and lasts 50 minutes. Counting back: 8:20 -> 8:00 is 20 minutes back; ___ more minutes back lands at the start, ___ ." -> 30 more minutes back; start = 7:30

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

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