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.

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.