Brain Teasers, a.k.a. The RTFQ Quiz by LuskT

Question 6

Another jogger is running along train tracks at 10 mph when he comes to a bridge 1 mile long. When he is 1/3 of the way across the bridge, he hears a train coming. Whether he keeps going forward or immediately turns around, if he maintains his speed he will get to the end of the bridge at the same time as the train. How fast is the train going?

30 mph