Math ?? non poker

[Scorpion]

Can someone help?

Charlie was crossing a narrow bridge. When he was halfway across he saw a car on the opposite side 200 yards away and heading toward him. He turned back and ran and barely made it before the car hit him. If Charlie had tried to cross the bridge the truck would have hit him 3 yards before he reached the end. How long is the bridge?

As near as I can figure there are 5 variables- the rate of the truck and Charlie and the time it takes for both of them to get whereever they are going and then the length of the bridge.