Spiderman has two close friends, Mary Jane & Gwen Stacy. After every mission, he rushes to the central subway. One line heads towards Mary's place, and another towards Stacy. Trains from each line leave every 10 minutes. Spiderman being impartial always boards the first train that leaves.
However, he observes that he ends up visiting Mary Jane nine times more often than Gwen Stacy. Can you decipher why?