A runner completes 1/4 of a 5 mile race every 8 minutes.at the same pace how far can the runner go in 16 minutes

The runner completes 1/4 of the race in 8 minutes, so in 16 minutes the runner can complete 1/4 + 1/4 = 1/2 of the race.

So, in 16 minutes the runner can complete 1/2 * 5 miles = <<1/2*5=2.5>>2.5 miles. Answer: \boxed{2.5}.