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avatar+1347 

It takes Mary $30$ minutes to walk uphill $1$ km from her home to school, but it takes her only $15$ minutes to walk from school to home along the same route. What is her average speed, in km/hr, for the round trip?

 Aug 13, 2023
 #2
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The answer is 4+4=8 by the segment addition postulate.

 Aug 13, 2023
 #3
avatar+129659 
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30 min = 1/2 hr

15 mn = 1/4 hr

 

Rate walking uphill  =   1  km/(1/2) hr =  2 km/ hr

Rate walking downhill = 1 km / (1/4) hr =  4 km/hr

 

Avg rate  when distance downhill = distance uphill  =   2 ( product of the rates) / (sum of the rates)  =

 

2 ( 2 * 4)  / ( 2 + 4)  =  16 / 6  = 8 / 3   =  2 1/3 km / hr

 

 

cool cool cool

 Aug 13, 2023

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