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Answer: 12 noon (assuming 12 hour analogue watches. 24 hour watches won't agree again until midnight tomorrow, when they will both say midday)
+1 hour apart each hour
12 hours apart after 12 hours
They say the same time at 12 noon (6 o'clock)
Night Watchmen
Age 11 to 14
ShortChallenge Level 
Answer: 12 noon (assuming 12 hour analogue watches. 24 hour watches won't agree again until midnight tomorrow, when they will both say midday)
| Time | Granny | Grandpa | Difference |
| 00:00 | 00:00 | 00:00 | 0 |
| 01:00 | 01:30 | 00:30 | 1 |
| 02:00 | 03:00 | 01:00 | 2 |
| 03:00 | 04:30 | 01:30 | 3 |
+1 hour apart each hour
12 hours apart after 12 hours
They say the same time at 12 noon (6 o'clock)
This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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