Suppose a giant meteor smashes into the earth and wipes out the majority of life. describe how succession would an ecosystem recover over time.

The asteroid that wiped out the dinosaurs 65 million years ago was about 10 (ten!) kilometers wide. That impact killed about 70% of all life forms on earth. It took several years before the Impact winter was over. It was THE game changer for mammalian evolution. WE are the result of that catastrophe...
BUT: You're talking about an asteroid which is a HUNDRED times larger in diameter than this specific one, thus a 100x100x100=1.000.000 more MASSIVE! Such a monster would effectively destroy ALL life on this planet. Human civilization would come to an end within a few hours. NO human could survive the unthinkable consequences of such  a catastrophe. 

The answer is 46,637.5