For each revolution, the satellite covers the circumference
of its orbit.
The circumference of a circle is (pi) x (diameter).
Since the satellite is 22,500 miles from the center, that number
is the radius of the circle. The diameter is 45,000 miles.
The circumference is (pi) x (45,000 miles) = 141,372 miles
The satellite's average speed is 141,372 miles per day, or
(141,372 / 24) = 5,890 miles per hour
relative to the center of the Earth.
