A train travels 40 km at a uniform speed of 30kmh−1. Its average speed after travelling another 40 km is 45kmh−1 for the whole journey. Its speed in the second half of the journey is
90 kmh−1
Let the speed of the train in later half =x, then the time taken to travel later 40 km =40x hours
Total time taken =4030+40x
Average speed = Total distanceTotal time=45
804030+40x=45
4x+120=8045×3x
x=90 kmh−1