Any more time saving approach?
Trains are leaving station A for station B every 15 minutes starting 8:00 am. The distance between the stations is 80 km. If a train leaves station B for station A at 11:05 am, how many oncoming trains will it meet. Trains travel in both directions at 40 km/h.
How would you solve this problem?
I get 16
Either train takes two hours to get to the destination.
Train B leaves at 11.05am. This means that it will meet all train A that did not reach station B before 11.05 am. It will meet anything after until it arrives at station A.
Since train A takes two hours to reach, if train A leave at 9.15am, then it will reach station B at 11.15am and will meet train B. If train A leaves at 9.00am, it will get there at 11.00am and won't meet train B. Therefore, we start counting from 9.15 am. and end at 1.00pm (since train B arrives at 1.05pm)
Every 15 mins including 9.15am to 1.00pm will get you 16 trains.