Answer
The average linear speed of the earth about the sun is $30~km/s$
Work Step by Step
Let the orbital radius be $1.5\times 10^{11}~m$
We can find the average linear speed of the earth about the sun:
$v = \frac{d}{t}$
$v = \frac{2\pi~r}{t}$
$v = \frac{(2\pi)(1.5\times 10^{11}~m)}{(365)(24)(3600~s)}$
$v = 30,000~m/s = 30~km/s$
The average linear speed of the earth about the sun is $30~km/s$
