How many centuries would it take for humans originating in Africa to travel to china some 10000 km away? at a rate of 1 km per year.

At an average rate of 1 km per year, it would take

10,000 years to migrate 10,000 km.

10,000 years = 100 Centuries

(Also, between 400 and 500 generations?)

This is an awkward funny question but nonetheless answerable. 10 thousand kilometers away at a rate of 1 km a year. thats 10 thousand years. and 10 thousand years is 100 centuries. 100 centuries is the answer.