Batteries

Hi, I have connected 3 batteries together to run a 48V motor, the batteries are 2 Turnigy 5.0 25-35c discharge 5 cell 18.5v and 1 Turnigy 5.0 25-35c discharge 3 cell 11.1v, will the bateries discharge at the same rate or will the smaller 3 cell run out quickier, people are saying the larger batteries my feed the smaller battery, but am not sure how that would happen regards Nathan