Any help would be much appreciated with this problem. The problem is: The rate of plate movement along portions of the Mid-Atlantic Ridge has been determined to be 3 cm/yr. At this rate how long will it take the Atlantic Ocean to widen another one kilometer? I think what you need to do is first change the the 3 cm/yr into km/yr and then go from there. But I'm not sure how to do that and what to do after that. Thank's in advance!