A faulty clock runs backwards and slow, covering $55$ minutes in a hour. ...

Question

The clock in the maths department common room is faulty. At twenty past three on Wednesday afternoon it shows 11:25. The clock in fact goes backwards, and is a bit slow, covering 55 minutes every hour. The clock has a usual 12 hour dial.

What time does it show at twenty past eight on the following Friday morning?

Answer 1

There is a total length of 41 hours between the first and second points where we are checking the clock. If the clocks goes backwards 55 minutes every hour, then it will go $55*41=2255$ minutes or $\dfrac{2255}{60}=37$ hours $35$ minutes. This gives a time of 9:50 on Friday morning.