Physics
posted by vv on .
Earth speeds along at 29.8 km/s in its orbit. Neptune's nearly circular orbit has a radius of 4.5 x 109 km, and the planet takes 164.8 years to make one trip around the Sun. Calculate the speed at which Neptune plods along in its orbit.

speed=distance/time=2PI*radius/164.8 years
now, convert years to seconds and you have it. 
yes i solve it like this but we will not need the speed of the earth ?