The Mean Velocity of the Earth in it's orbit around the Sun is approximately 29.78 km/s
The Earth travels in nearly circular path around the Sun. The mean radius of that circle is called an Astronomical Unit (ua). Using the simple formula for the circumference of a circle:
`C = 2 * pi * r`
we can compute the distance travelled in a year. Doing the math, where velocity is distance decided by time, we can compute the velocity:
`v = (2*PI*r)/(1 year)`
Now, we just have to convert astronomical units per year into kilometers per second to get 29.784735696231 km/s.