>>On your daily drive to work, there's a small hill. You have to drive up one side, then down the other.
>>
>>Because you're cheap green, you don't want to use any more fuel than necessary in getting over the hill. After running a few tests, you've discovered that if you approach the bottom of the hill at exactly 50 km/h, you can knock your vehicle out of gear, switch off the engine, and coast to the top. That gives you just barely enough speed to start coasting down the other side, when after which you can switch your engine back on and put it back in gear.
>
>Disregarding the question entirely - but why, if attempting to save fuel, would you start the engine when coasting downhill ?

Lawyers dwell on small details ... :)

>>One day, though, you're not paying close attention to your speed. When you shift into neutral and switch off your motor at the bottom of the hill, you notice you're going 60 km/h instead of 50 km/h.
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>>How fast will you be going at the top of the hill?
>>
>>(techie types: ignore differences in aerodynamic drag and rolling resistance)