A car drives a 180 km route in three equal stretches of 60 km, taking them at 30 km/h, 40 km/h and 60 km/h respectively. Its average speed over the entire 180 km (in km/h) is:

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Accepted Answer

40. Times taken = 60/30 + 60/40 + 60/60 = 2 + 1.5 + 1 = 4.5 hours for 180 km. Average speed = 180/4.5 = 40 km/h. (The plain average of 30, 40 and 60 is 43.33 — wrong, because the legs take different times.)

A car drives a 180 km route in three equal stretches of 60 km, taking them at 30 km/h, 40 km/h and 60 km/h respectively. Its average speed over the entire 180 km (in km/h) is:

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