The average speed of a train is 20% less on the return journey than on the onward journey. The train halts for half an hour at the destination station before starting on the return journey. If the total time taken for the to and fro journey is 23 hours, covering a distance of 1000 km, the speed of the train on the return journey is

Let the onward speed of the train be s km/hr, which makes the return speed 0.8s. The total travel time of 22.5 hours (subtracting the 0.5-hour halt from the 23-hour total) equals the sum of the onward and return times for the 1000 km round trip, giving the equation 500/s + 500/(0.8s) = 22.5. Solving this equation yields the onward speed as 50 km/hr, meaning the return speed is 40 km/hr.

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