Question

A train travel 40 km at a uniform speed of 30 km hr. It's average speed for the whole journey after travelling another 40 km is 45 km h. It's speed in the second half of the journey is.​

Answer 1

Answer:

the train travelled at 90km/h

Explanation:

the train travelled 40km at 30km/h

=> time taken = 40/30h = 4/3h

the train travelled 40km at say x km/h

=> time taken = 40/x h

average speed = total distance / total time

=> average speed = 40+40 / (4/3)+(40/x) = 80 / (4x+120)/3x

=> 45 = 80×3x / (4x+120)

=> 3 = 16x / (4x+120)

=> 12x+360 = 16x

=> 4x = 360

=> x = 90