Plate Tectonics: Calculating Collision Time for Distant Continents

[CrossFit415]

Typical motions of one plate relative to another are 1 centimeter per year. At this rate, how long would it take for two continents 3,000 km apart to collide?

I don't know where to start or what formula to use.

 

[zhermes]

How is this astronomy?

Well, if a car is going 10 mph, how long would it take to travel 200 miles?
How can you generalize that problem, to your problem?