Puzzle a Day!

Using illustrative numbers (highlight the blank spaces to see my working):

If Peter runs 100 yards in 100 seconds then he has taken 10 seconds for every 10 yards, and Mary must have run 90 yards in 100 seconds or 11.1 seconds for every 10 yards

Therefore Peter runs 110 yards in 110 seconds
Mary runs 100 yards in 100 + (100/9) = 111 seconds

So my answer is Peter would still win. Of course, my maths (or English comprehension) skills may be way off after a long day! However, there's not an easy way to gently hint at an answer that's one thing or the other, so I've done my best at a spoiler box!