Calculating Orbital Velocity and Period Using Kepler's Laws

[DEckrich7]

Homework Statement

A ship is in orbit 155 mi. above the earth, (a) what is its velocity? (b) How long will it take the ship to orbit the earth?

Homework Equations

v=(G*(m/r))^.5, (2*PI*r)/T=v

The Attempt at a Solution

I added 155 mi to 3963 mi and got 4118 mi and that is about 6627359 m, which is how high the ship is from the center of the earth. I plugged that into the first equation I gave, and got a velocity of about 7757.8 m/s, which seems pretty logical to me. However, I'm not sure about the time. I solve for T in the second equation (ex. (2*PI*6627359)/7757.8) and get about 5367.6 seconds, about 1 hour and 30 minutes, and that seems way to short. Any ideas on where to point me?
Thanks in advanced :)

 

[Delphi51]

I found the period directly.
Fc = Fg
4π²mR/T² = GMm/R²
T² = 4π²R³/(GM)
Using R = 6619448 m I got T = 5358 s.
It is a reasonable time.