Ok John cycles from Norwich to London at 15 mph .

The distance is 100 miles.

Geraldine takes the car and ,at a steady speed of 45 mph leaves at the same time as John .

She arrives in London ahead of John ,turns around instantly and follows the same back path to Norwich.

She meets John en route.

How long after John has left Norwich does he encounter Geraldine?

Especially what is the formula for getting the answer.

And what is the formula if all we know is that Geraldine's speed is "r" times faster than John's?

thanks!