Query about Question 4 from "PrepSwift: Three Ringing Bells" [3569]

https://prepswift.gregmat.com/quizzes/quiz/prepswift-three-ringing-bells (Question 4)


how trains to CX will stop at Orpingdon at 8:15,8:30 and trains to VIC will stop at Orpingdon at 8:35 9:05. is it because that there is delay of 5 minute between them.I didnt understand

The case they described is if VIC train gets 5 minutes late, instead of departing at 8:00, it is now departing at 8:05 … So it will never meet the other train CX, which has already departed at 8:00 and will follow the time schedule of departing every 15 minutes which is 8:15, 8:30, 8:45 and then 9:00 ….