Tick tock
Tick's watch is slow and Tock's watch is fast. How long is it before their watches differ by an hour?
Age
11 to 14
Challenge level
Problem
Tick's watch runs 2 minutes per hour too slow.
Tock's watch runs 1 minute per hour too fast.
They set them to the same time at midday on Sunday.
The next time they met, one of the watches was one hour ahead of the other.
What was the earliest time this could have been?
Student Solutions
Answer: 8 am on Monday
Tick's watch is 2 minutes slow per hour, Tock's is 1 minute fast per hour, so Tock's watch is faster than Tick's watch by 3 minutes per hour.
| Correct time | Tick's Watch | Tock's Watch | Difference |
|---|---|---|---|
| 12:00 | 12:00 | 12:00 | - |
| 13:00 | 12:58 | 13:01 | 3 minutes |
| 14:00 | 13:56 | 14:02 | 6 minutes |
They get 3 minutes further apart after each 1 hour.
They will be 60 minutes further apart after 20 hours.
20 hours after midday on Sunday is 8 am on Monday.