A train leaves station X at 5am and reaches station Y at 9am. Another train leaves station Y at 7am and reaches station X at 10:30 am. At what time do the two trains cross each other?

A.

7:36 am

B.

7:56 am

C.

8:36 am

D.

8:56 am

• The answer is a, 7:56 am
  
  Assuming that the total distance is 1 kilometer or 1000 meter,
  
  the speed of train A is 1000m/4 hours = 1000m/240 minutes or 4.1667 meters/minute
  
  The speed of train B is 1000m/3.5 hours = 1000m/210 minutes or 4.7619 meters/minute
  
  At 7:00 am, we know that train A is already halfway to Station B, while train B is stiil stationary.
  
  Distance = Speed multiply by time ( D = S x T)
  
  At 7:45 am, train A will be at distance
  4.1667m/minute x 165 minutes ( 2 hours & 45 minutes) = 687.50 meters from Station A, while train B will be at
  4.7619 m/minutes x 45 minutes = 214.285m from Station B or
  785.715 meters ( 1000 meter - 214.285 meter) from Station A, which means they did not meet at 7:45 am.
  
  At 7:56 am., train A will be at 4.1667 meters/minute x 176 minutes ( 2 hours & 56 minutes) = 733.33 meters from Station A.
  At 7:56 am, train B will be at 4.7619 meters/minute x 56 minutes = 266.67 from Station B or 733.33 meters (1000 meters - 266.67 meters) from Station A. It is at this time - 7:56 am, that the two trains met each other.
  
  At this time, I am still figuring out the correct equation, if there is.
• 8 years agoHelpfull: Yes(0) No(0)
• 5-9 = 4 hrs
  7-10:30 = 3.5 = 3 1/2 = 7/2
  
  2/7+1/4= 15/28..speed
  
  half distance already covered.
  28/2 = 14
  time = 14/15*60 = 56 mins
  7 hrs + 56 mins
  7:56 AM
• 8 years agoHelpfull: Yes(0) No(0)