Arc length formula: l = π rn/ 180. Here we know that the speed of a train passing through an arc is 10m/s (which can be converted from 36km/ h to speed per second), and if 10s passes, the arc length is 100m. The radius is 300 meters, and it is substituted into the formula:

100=(π×300×n)÷ 180

π×300×n= 18000

π×n=60

n≈ 19. 1