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Inge is competing in a 400 m race. She runs at a constant speed of 4.6 m/s for the first 150 m, then 4.2 m/s for 40 seconds. The remainder of the race takes her 38 seconds to complete. What is Inge's average speed for the entire race to 1 dp?

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sqdancefan

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Answer:

  3.6 m/s

Step-by-step explanation:

To find Inge's average speed for the race, we need to know her total distance (400 m) and her total time. The times for the 2nd and 3rd portions of the race are given, but we need to figure the time for the first portion. That will be ...

  time = distance/speed

  time = (150 m)/(4.6 m/s) = 32.609 s . . . . time for first 150 m

Then Inge's average speed is ...

  (400 m)/(32.609 s + 40 s + 38 s) = (400 m)/(110.609 s) ≈ 3.6 m/s

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