Traveling at 50 yards per minute, Biff can travel 500 yards in 500/50=<<500/50=10>>10 minutes.
In 10 minutes, traveling at 51 yards per minute, Kenneth can travel 10*51=<<10*51=510>>510 yards.
Thus, Kenneth will be 510-500=<<510-500=10>>10 yards past the finish line when Biff crosses the finish line.
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