1.
A kitchen clock runs 15 minutes slow. It shows 3:40. What is the real time?
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Answer:
Did you know? Before railways, every town kept its own local time by the sun — noon in one town was not noon in the next.
2.
A tower bell strikes the hour: once at 1 o'clock, twice at 2 o'clock, and so on. How many strikes altogether from 1 o'clock through 6 o'clock?
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Answer:
Did you know? We split hours into 60 minutes because the Babylonians counted in sixties, more than 4,000 years ago.
3.
A clock chimes every 15 minutes. How many chimes are there from 2:00 to 4:00, counting the chimes at 2:00 and at 4:00 themselves?
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Answer:
Did you know? A sundial only works in sunshine, which is why water clocks were invented — they kept counting at night and indoors.
4.
Three friends arrive at the clock tower. Idris arrives before Salma. Yahya arrives after Salma. Who arrived first, and who arrived last?
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Answer:
Did you know? The pendulum clock, invented in 1656, was such a leap that it cut a typical clock's daily error from minutes to seconds.
1.
You have a 4-minute hourglass and a 7-minute hourglass, and nothing else. How do you measure exactly 9 minutes? Write the steps with the times.
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Answer:
Did you know? Working out longitude at sea needed a clock that stayed accurate on a rolling ship — the problem stood for decades.
2.
Three bells ring together at noon. One rings every 6 minutes, one every 8 minutes, one every 12 minutes. How many minutes until all three ring together again?
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Answer:
Did you know? An atomic clock is so steady it would drift less than a second over millions of years.
3.
A train arrives at 3:45. The journey took 1 hour 50 minutes, and before boarding he waited 25 minutes at the station. What time did he reach the station?
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Answer:
Did you know? Railways forced countries onto standard time — trains cannot run to a timetable if every town keeps its own clock.
4.
At 4:20, what is the angle between the hour hand and the minute hand? (Careful: by 4:20 the hour hand has already crept past the 4.)
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Answer:
Did you know? A clock face is 360 degrees over 12 hours, so the hour hand moves just half a degree every minute.
3rd Grade
1. 3:55.
Slow means it hasn't caught up yet, so the real time is later: 3:40 + 15 minutes = 3:55. Ask which way before adding — that's the whole question.
2. 21 strikes.
1 + 2 + 3 + 4 + 5 + 6 = 21. Pair the ends to go faster: (1+6) + (2+5) + (3+4) = 7 + 7 + 7.
3. 9 chimes.
2:00 to 4:00 is 120 minutes, and 120 ÷ 15 = 8 gaps. Counting both ends means 9 chimes, not 8 — fenceposts, not fences.
4. Idris first, Yahya last.
Idris before Salma, and Salma before Yahya, chains into Idris → Salma → Yahya. So Idris first and Yahya last.
4th Grade
1. Yes — 9 minutes, using four flips.
Start both at 0. At 4 min the small one empties — flip it. At 7 min the big one empties — flip it. At 8 min the small one empties again; the big one has now been running 1 minute, so it holds exactly 1 minute of sand in the bottom. Flip the big one and it runs out at 9 minutes. The idea: a part-used glass measures the time it has already run.
2. 24 minutes.
Find the first number 6, 8 and 12 all divide into. Multiples of 8: 8, 16, 24. 24 is divisible by 6 and 12 too, so 24 minutes.
3. 1:30.
Work backwards from the arrival. 3:45 − 1 h 50 min = 1:55 departure. Then 1:55 − 25 min = 1:30. Undo the journey first, then the wait.
4. 10 degrees.
Minute hand: 20 min × 6° = 120°. Hour hand: 4 × 30° = 120°, plus 20 min × 0.5° = 10°, so 130°. Difference = 10°. Answering 20° means forgetting the hour hand drifts.