Why was an attack against vicksburg by river just not possible for union forces?

This size running track is usually called a 400 meter track. however if a person ran as close to the inside as possible on the track they would run less than 400 meters in one lap. how far away from the inside border would someone have to run to make one lap equal exactly 400 meters

The population in a city is modeled by the equation p(d)= 100,000*(1+0.3) where d is the number of decades since 1970

What states a rule using variables expression term or formula