A train travels 75 kilometers in 3 hours, and then 66 kilometers in 1 hours. What is its average speed?

Initial distance (D1) : 75 Km

Time taken to cover this distance = 3 hrs.

Speed = Distance / time

Speed1 = 75/3 = 25Km/hr

Later the train travels

Distance (D2) : 66 Km

Time taken to cover this: 1hr

Speed = Distance/time

Speed2 = 66/1 = 66Km/hr

Average speed = (speed1 + speed 2) / 2

Average speed = (25+66) / 2

Average speed = 45.5 Km/hr