The usually train between 15 hours a week and 20 hours a week, just running. They spend a lot of other time on conditioning and other training.
there is 12 runners in an olympic relay race
Alot. I am a runner and I train about 3 hours every day, even on week ends, you have to be commited to it.
US Olympians train at least 6 hours per day minimum.
at least 16 hours a day
US Olympians train at least 6 hours a day and i imagine if they want to they might go more. Maybe 6-8 hours a day.
Olympic Rowers train 4 to 5 hours per day, six days a week. that time includes only time spent at heart rate above 145. Stretching and rests take 1hour. So its 5-6 hours per day all together.
100 metres in 10 seconds
This answer depends on the competitive level of the athelete at hand. Anywhere between 10-30 hrs for competitive swimmers
it takes around 9 hours (overnight train)