Question

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16. At 12 noon my watch was correct. However, it then started to lose 18 minutes
per hour. Four hours ago it stopped completely and is now showing the time as
15.30. What is the correct time?

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Answer 1

At 12:00 it was correct, so after that the hours were 18 minutes shorter because it says that the watch lost 18 minutes per hour.

We'll note one hour with x.

12:00 + 42/60 x +4x=15:30

Because one hour has 60 minutes, then 30 minutes means 1/2 hour, so 15:30 means 15,5

12+42/60x+4x=15,5

After solving this ecuation you'll find x= 35/47, which means that there around 9,5 hours lost.