How fast does the earth orbit the sun?
The average speed is 29.7848 km/s. It is maximum at perihelion and minimum at aphelion. My simple expression for orbit velocity at a distance r is 29.7848 X square root ( (2r - a)/r) km/s.
At perihelion, it is 30.2867 km/s. At aphelion, it is 29.2112 km/s..