A runner completes two laps around a 400-m track. She runs the first lap in 1 min 32 s, and the second lap in 1 min 49 s. What is her average speed?

The average speed is 3.98

Explanation:

Speed is a scalar quantity that shows the relationship between the distance traveled and the time taken.

In other words, speed is a scalar quantity that determines the ratio of the distance traveled by a body or object and the time it takes to cover that distance. Speed does not take direction into account.

Average speed refers to the total distance traveled during a given time, which is equivalent to saying that it is the ratio of distance and time.

In this case you know that a runner completes two laps around a 400 m track, so the total distance traveled is 800 m.

On the other hand, you know that the runner completes the first lap in 1 min 32 s, and the second lap in 1 min 49 s. Being 1 min equivalent to 60 s, the first round is completed in 92 s and the second round in 109 s. So the total time to complete the two laps around the track is 92 s + 109 s = 201 s.

That is, being:

and replacing in the definition of average speed:

you get:

average speed= 3.98

The average speed is 3.98

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