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am, pm & Duration

Maths · Y3 Time
Year 3
Lesson Guide
Explanation
A day has 24 hours, but the clock face only shows 12 — so the hands go around TWICE. To tell the two laps apart we use am (midnight to midday) and pm (midday to midnight). Breakfast at 7 is 7 am; dinner at 7 is 7 pm — same clock picture, different halves of the day. Midday itself is 12 pm, midnight is 12 am.
Your Turn
am or pm? School starts. You brush teeth before bed. Saturday cartoons. Check: am (about 9), pm, am.
Watch Out
The 12s are the confusing pair: midday = 12 pm, midnight = 12 am. (Trick: pm starts AT midday.)
Explanation
Duration is how much time passes between a start and a finish. Soccer practice from 3:00 to 3:45? Count along a time line in easy hops: 3:00 → 3:15 → 3:30 → 3:45 — three hops of 15 minutes = 45 minutes. A time line works exactly like a number line, and hopping beats guessing every time.
Your Turn
How long is 4:00 to 4:30? And 6:15 to 6:45? Check: 30 minutes, and 30 minutes.
Watch Out
Duration is a length of time, not a clock time. The answer is '45 minutes', never '3:45'.
Explanation
When the time crosses an hour, use the o'clock as a stepping stone — exactly like bridging to 10 in addition! From 2:40 to 3:20: first hop to 3:00 (that's 20 minutes), then hop on to 3:20 (20 more). Total: 40 minutes. Two easy hops instead of one confusing calculation.
Your Turn
How long from 5:50 to 6:15? Check: 10 min to 6:00, then 15 min → 25 minutes.
Watch Out
Never subtract clock times like ordinary numbers — 3:20 − 2:40 is NOT '80'. Hop through the hour instead!
Explanation
Sometimes you know the start and the duration and need the FINISH. A movie starts at 4:30 and runs 1 hour 20 minutes: add the hours first — 4:30 + 1 hour = 5:30 — then the minutes — 5:30 + 20 = 5:50. If the minutes climb past 60, they roll into a new hour: 5:45 + 30 minutes goes 15 to reach 6:00, then 15 more → 6:15.
Your Turn
Practice starts 3:15 and lasts 45 minutes. When does it end? Check: 3:15 + 45 = 4:00 exactly.
Watch Out
Minutes roll over at 60, not 100! 5:45 + 30 is 6:15, never "5:75".
Explanation
Your whole day is a timetable of am and pm times, and durations connect them. How long is school, 8:30 am to 3:00 pm? Hop in big pieces: 8:30 to 12:30 is 4 hours, 12:30 to 3:00 is 2 hours 30 — total 6 hours 30 minutes. Try timing your own day: wake-up to school, school to dinner. Quiz and exercises time!
Your Turn
You sleep 8:30 pm to 7:00 am. How long? Check: 8:30 → 12:00 midnight is 3 h 30, then → 7:00 is 7 h. Total 10 h 30 min!
Watch Out
Crossing midday or midnight? Use 12:00 as your stepping stone, and mind the am/pm switch.
Step 1: Introduction
Step 1 of 5
The day has 24 hours — the clock only 12! 🌅 am = midnight → midday 7 am breakfast 10 am recess 🌙 pm = midday → midnight 3 pm home time 7 pm dinner The clock goes around TWICE each day. 7 am and 7 pm look identical on the clock — am/pm tells them apart. 12:00 midday = 12 pm · 12:00 midnight = 12 am
From 3:00 to 3:45 3:00 3:15 3:30 3:45 15 min 15 min 15 min Duration = the time BETWEEN start and finish. 3:00 to 3:45 = three 15-minute hops = 45 minutes. Count along a time line, just like a number line!
From 2:40 to 3:20 2:40 3:00 3:20 20 min to the hour 20 min past it Hop to the o'clock first, then keep going. 2:40 → 3:00 is 20 min. 3:00 → 3:20 is 20 min. Total: 40 minutes. The o'clock is your stepping stone — just like bridging to 10!
Movie starts 4:30, runs 1 hour 20 min 4:30 → +1 hour → 5:30 → +20 → 5:50 Add the HOURS first, then the MINUTES. 4:30 + 1 hour = 5:30. Then 5:30 + 20 min = 5:50. The movie ends at 5:50. If minutes pass 60, roll into the next hour: 5:45 + 30 min = 6:15.
A day in times 📅 7:00 am wake up 🌅 8:30 am school starts 🏫 3:00 pm school ends 🎒 7:30 pm dinner 🍽 School day: 8:30 am → 3:00 pm = 6 hours 30 minutes! Hop: 8:30 → 12:30 is 4 h, 12:30 → 3:00 is 2 h 30 min.
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