753.9822368615503771848 meters

How i did it:

50*2*pi+(70*pi*2)

For one it is just 2*r*pi so 50*2*pi, that is:314.1592653589793238

The SMALLER one has a DIAMETER of 50 meters

circumference = pi x dia

pi x50 =

pi*50 = 157.0796 meters