FINDING THE AVERAGE SPEED IN ROUND TRIP

What is round trip?

Travelling in one direction at a certain rate of speed, and then returning along the same route at a different rate of speed is known as round trip.

Finding Average Speed

Example 1 :

Mr. Brown drove at a speed of 96 km/hr to his office every morning. He returned from work at the speed of 72 km/hr. What was his average speed for the round trip?

Solution :

In both the ways, Mr. Brown covers the same distance.

Formula to find the average speed :

= 2xy/(x + y)

Substitute x = 96 and y = 72.

Average speed = (2 ⋅ 96 ⋅ 72)/(96 + 72)

= (2 ⋅ 96 ⋅ 72)/168

= (96 ⋅ 72)/84

= (8 ⋅ 72)/7

= 576/7

= 82.3 km/hr

Example 2 :

Mr. John drives at a constant speed of 108 km/h to his office every morning. He drives at a constant speed of 72 km/hr. for his return trip. What is his average speed for the round trip?

Solution :

In both the ways, Mr. John covers the same distance.

Average speed = 2xy/(x + y)

Substitute x = 108 and y = 72.

= (2 ⋅ 108 ⋅ 72)/(108 + 72)

= (2 ⋅ 108 ⋅ 72)/180

= (108 ⋅ 72)/90

= (6 ⋅ 72)/5

= 432/5

= 86.4 km/hr

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