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If you run for 0.4 hours at 7 mph, how fast should you walk during the next 0.8 hours to have the average speed of 5 mph?

 Feb 23, 2020
 #1
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0.4 x 7 mph =2.8 miles - distance run.
Let the required speed =S
[2.8 + 0.8S] / [0.4+0.8] =5, solve for S
S =4 mph - must walk to attain an average of 5 mph, or:
6 miles / 1.2 hours =5 mph

 Feb 23, 2020
 #2
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.4*  7 m/h   +  .8 *  x  m/h

_________________________

       .4  +  .8      hr                                       = 5 m/h

 

 

 

2.8  + .8x   = (1.2) 5

.8x = 3.2

x= 4 m/hr

 Feb 23, 2020

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