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(a) There was terrible traffic on the highway, and Kiran drove to work at 15 miles per hour. How
fast would he need to drive home for the average speed for his round trip commute to be 35
miles per hour?
(b) Seetha drove to work at 30 miles per hour. How fast would she need to drive home for the
average speed for her round trip commute to be 40 miles per hour?

 Oct 24, 2022
 #1
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(a) 60 miles per hour

 

(b) 72 miles per hour

 Oct 24, 2022
 #2
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(a)  Let his average speed driving home=S

 

When the distance back and forth is the same, then:

 

Average speed =Harmonic mean

 

[2 x S x 15] / [S + 15] =35, solve for S

 

S = - 105 mph ??! - Not possible. You average speed must be less than 30 mph. Check your numbers carefully.

 

 

 

(b) [2*30*S] / [30 + S] ==40, solve for S

 

S ==60 mph

 Oct 24, 2022

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