A Transport bus started Madurai Bus Terminal at 7 am and travelled at an average speed of 40 km per hour till 8.30 am. This bus stopped at the on-way hotel for breakfast till 9 am and travelled at an average speed of 30 km per hour thereafter till its destination. Another express bus started from Madurai at 11 am and travelled at an average speed of X km per hour. The Express bus crossed the transport bus at 5 pm on the same day. Find the value of X?

a)60 km/hr b)40 km/hr c)20 km/hr d) 50 km/hr

• d) 50 km/hr
  
  Transport bus travelled at average speed of 40 km/hour
  For 1 1/2 hours (i.e from 7 am till 8.20 am) Distance covered = 60 km.
  Express bus starts at 11 am.
  Till the express bus starts, transport bus would have covered further distance of
  30 x 2 = 60 km.
  
  Total distance covered upto 11 am by Transport bus is 60 + 60 = 120 km
  Transport bus is travelling further at an average speed of 30 km per hour.
  Express bus crossed Transport bus at 5 pm after travelling for 6 hours
  
  Distance covered by the Transport bus till 5 pm = 120 + 180 = 300 km
  This distance of 300 km is covered by express bus in 6 hours.
  Hence average speed of Express bus = X = 300/6 = 50 km/hour
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