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Suzette ran and biked for a total of 110 mi in 7 h. Her average running speed was 5 mph and her average biking speed was 20 mph. Let x = total hours Suzette ran. Let y = total hours Suzette biked. Use substitution to solve for x and y. Show your work. Check your solution.

(a) How many hours did Suzette run? 1.5 hours of running

(b) How many hours did she bike? 2 hours of biking

 Aug 21, 2019
 #1
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x  +  y  = 7       rearrange as   y  = 7 - x   (1)

 

And using

 

Rate * Time  = Distance    we have  that

 

5 * (x)  + 20 (y)   =   110     (2)

 

Sub  (1)  into (2)  for   y  and we have that

 

 

5 * (x)   + 20  ( 7 - x)  =  110       simplify

 

5x + 140  - 20x   =  110

 

-15x  + 140  = 110      subtract 140 from both sides

 

-15x  =  - 30      divide both sides by - 15

 

x  = 2  hours running

 

And   7 - x  = 7 - 2   =    5 hours biking

 

 

 

cool cool cool  

 Aug 21, 2019

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