The circumference of the small ring is

1÷40= 1/40

So the circumference of the big ring is

1÷30= 1/30

Their circumference difference is

1/30- 1/40= 1/ 120

So, the whole journey is

10 ÷1120 =1200 (cm)

1200m =12m

Answer: This distance is 12 meter.