You are driving to a mate's house.

You need to arrive at 3pm. If you drive at 100km/h you will arrive 15 minutes early. If you drive at 80km/h you will arrive 15 minutes late.

1. What time did you leave at?
2. What speed should you drive at to be on time (rounded to a whole number)?
3. How far away does your mate live?

Answer later unless someone gets it first. (Hint: simultaneous equations or a graph.)

Update: I fixed question 1 which was a bit loose (changed from "should" leave to "did" leave).