twelve posts stand equidistant along the stadium. starting at the first post, a runner reaches the eight post in 8 seconds. if he runs at a constant rate, how many seconds are needed to reach the twelfth post?

Answer 1

To move the seven post-to-post distances (1 to 8) requires 8 seconds. That is 8/7 sesonds per interval. To run 4 more intervals at the same speed requires 4* 8/7 = 4.57 s more time, for a total (from the beginning) of 12.57 s