Question 15
Four one-way tram lines run as shown.
Line A departs A every 3 minutes; B departs B every 2; C departs C every 4; D departs D every 5. Their first departures of the day are simultaneous. Edge numbers are travel times in minutes between circular stops; stopping time is negligible. Passengers may transfer at common stops, sometimes waiting for the next tram. Marcus wants the fastest route from home to the theatre (“Rạp hát”). How many stops does he pass, including A and the theatre stop, and what is the minimum time?
Editorial timing convention: Marcus boards the first A departure at the common start time, taken as minute 0.
Line A departs A every 3 minutes; B departs B every 2; C departs C every 4; D departs D every 5. Their first departures of the day are simultaneous. Edge numbers are travel times in minutes between circular stops; stopping time is negligible. Passengers may transfer at common stops, sometimes waiting for the next tram. Marcus wants the fastest route from home to the theatre (“Rạp hát”). How many stops does he pass, including A and the theatre stop, and what is the minimum time?
Editorial timing convention: Marcus boards the first A departure at the common start time, taken as minute 0.