Calculate the average speed of a complete round trip in which the outgoing 300 km is covered at 93 km/h, followed by a 1.0-h lunch break, and the return 300 km is covered at 56 km/h. Express your answer to two significant figures and include the appropriate units.

Answer : 63 km/h

Explanation:

Outgoing distance = 300 km.

Outgoing speed = 93 km/h.

Break time = 1 h

Return distance = 300 km

Return speed = 56 km/h

Outgoing time = outgoing distance / outgoing speed

Outgoing time = 300 km / 93 km/h = 3.225806451612 h

Return time = return distance / return speed

Return time = 300 km / 56 km/h = 5.357142867142 h

Total distance =. Outgoing distance + return distance travelled

Total distance = 300 km + 300 km = 600 km

Total time = outgoing time + break time + return time

Total time = 3.225806451612 h + 1 h + 5. 357142867142 h = 9.582949308754 h

Average speed = total distance / total time

Average speed = 600 km / 9.582949308754 h

Average speed = 62.61120462042 km/h = 63 km/h