A person traveled 4 sides of the triangle with speed of a 100, 200, 300, 400 km/hr. What is the average speed of the whole journey?

The average speed for the journey is the distance of the journey divided by the time taken. If each leg is the same length, the average will be
  4/(1/100+1/200+1/300+1/400)
  = 4/(12/1200+6/1200+4/1200+3/1200)
  = 4*1200/(12+6+4+3)
  = 4800/25
  = 192
The average speed is 192 km/hr.

Dude, you REALLY need to brush up your geometry.
A triangle doesnt have 4 sides. =|