that's freakin easy that's 10 sets of 10 pushups in one day? that's not hard even for me who never exercises.
now I can't do more than 20 pushups at once. I wouldn't be able to do 100 pushups at once if that is what you mean.
When I was locked up, I was doing 1000 in under 40 mins-- I swear by them..cardiovascular and also muscle training-- Can't beat it!!
pushups on their own are pretty useless. go for a nice walk/jog for 2-5 miles for 3 times a week continously. running is the best excercise there is.