Question 878425
10km is equivalent to ~6.2137 miles
He runs ~6.2137 in 42 minutes.  How many in 60 minutes?
{{{6.2137/42}}}={{{x/60}}}
x = 8.8767 mph
.
If he can run 8.8767 miles in one hour, how long does it take to run 4 miles?
4/8.8767 = 0.45 of an hour
60 minutes in an hour, so 60*.45 = 27 minutes

(numbers are rounded, so it's an approximation)