An express runs 180 km at 90 km/h. On the way back it covers half the distance at 45 km/h and the other half at 90 km/h. What is its average speed for the round trip?

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Accepted Answer

72 km/h. Times: out 2 h; back 90/45+90/90=3 h. Average =360/5=72 km/h. (75 km/h averages the speeds instead of using total time.)

An express runs 180 km at 90 km/h. On the way back it covers half the distance at 45 km/h and the other half at 90 km/h. What is its average speed for the round trip?

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