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Jan walks 2 miles at a constant rate of 3 miles per hour and then runs 1 mile at a constant rate of 8 miles per hour.(a) What is Jan’s average speed for the entire trip?
(b) Is the average speed in part (a) equal to the average of Jan’s two speeds?

 Feb 7, 2021
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distance / time = average speed

 

distance = rate * time

 

     time = distance/rate

 

(2 miles + 1 mile)    /   (2 miles/3 m/hr   + 1 mile/ 8 m/hr)

 

3  / (2/3 + 1/8)  = 3   /    (16+3)/24   = 3 * 24/19 = 3.79 m/hr avg

 

 

 

b) no  =====>  ( 3 + 8)/2 = 5.5 m/hr   does not equal   3.79 m/hr

 Feb 7, 2021

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