Solving Physics Time Problem: Apollo Lunar Landing Mission

[mathcrzy]

1. Homework Statement

During an Apollo lunar landing mission, the command module continued to orbit the Moon at an altitude of about 104 km. How long did it take to go around the Moon once?

2. Homework Equations

T^2=[4pi^2(r)]/g

3. The Attempt at a Solution

square root of 4pi^2(7.35e25+104000)/9.8=1.7e13min. this answer does not make sense though

 

[Avodyne]

Where does the 7.35e25 come from?