To calculate the average speed of the runners in the 400-meter relay, we first need to find the total time taken by all the runners and the total distance they ran.
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Total Distance: The total distance for the relay is 400 meters since each of the 4 runners runs 100 meters.
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Total Time:
- First runner: 15 s
- Second runner: 17 s
- Third runner: 15 s
- Fourth runner: 13 s
Total time = 15 s + 17 s + 15 s + 13 s = 60 s
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Average Speed: The average speed is calculated using the formula:
\[ \text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}} \]
Substituting the values we have:
\[ \text{Average Speed} = \frac{400 \text{ m}}{60 \text{ s}} \approx 6.67 \text{ m/s} \]
So the average speed of the runners is 6.7 m/s.