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Julia ran and bikes for a total of 40 miles in 5.8 hours.  Her average running speed was 5.5 mph.  Her average biking speed was 13.5 mph.  

Let x = total hours Julia ran

Ley y = total hours Julia biked

 

Use substitution to solve for x and y.SHOW ALL WORK.Round answers to nearest tenth.

 

  1. How many hours did Julia run?
  2. How many hours did Julia bike?
 Sep 11, 2018
 #1
avatar+100587 
+2

We have that

 

x + y  =  5.8  ⇒    y  = 5.8 - x    (1)

 

And note that rate  * time  = distance covered.....so..

 

5.5x + 13.5y  = 40    (2)      put (1)  into (2)  for  y   and we have

 

5.5x + 13.5(5.8 - x)   = 40    simplify

 

5.5x  + 78.3  - 13.5 x   =  40

 

-8x + 78.3  = 40       subtract  78.3 from both sides

 

-8x  = - 38.3      divide both sides by  -8

 

x ≈  4.8  hrs  running

 

And  y ≈  5.8 - x  =  5.8 - 4.8  ≈  1 hrs biking

 

 

 

cool coolcool

 Sep 11, 2018

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