SOLUTION: A runner splits her journey into two parts. She travels at a speed of v m/s for t seconds and covered a third of the journey. Then she continued the rest of her journey at twice

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A runner splits her journey into two parts. She travels at a speed of v m/s for t seconds and covered a third of the journey. Then she continued the rest of her journey at twice      Log On


   

Question 825483: A runner splits her journey into two parts. She travels at a speed of v m/s for t seconds
and covered a third of the journey. Then she continued the rest of her journey at twice
the speed. Express in terms of v and t her average speed.
Answer by TimothyLamb(4379) About Me  (Show Source):
You can put this solution on YOUR website!
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s = d/t
d = s*t
t = d/s
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part 1:
t1 = (1/3)d/v
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part 2:
t2 = (2/3)d/2v
---
total trip average speed:
t = t1 + t2
s = d/t
s = d/( (1/3)d/v + (2/3)d/2v )
s = d/( (1/3)d/v + (1/3)d/v )
s = d/( (2/3)d/v )
s = 1/( (2/3)/v )
s = v/(2/3)
---
answer:
s = (3/2)v
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