Respuesta :
Speed is the rate at which a body changes its position. The speed by which Marina runs is 4 miles/ hr.
What is Speed?
Speed is the rate at which a body changes its position. It is given by the formula,
[tex]\rm{Speed = \dfrac{Distance}{Time}[/tex]
Given to us
Marina can bicycle 19. 5 miles at the same time it takes her to run 6 miles.
Marina bikes 9 miles per hour faster than she runs.
Let the speed of the Marina running be s, and the time is taken to run 6 miles be t.
Time is taken by Marina to cover a distance of 6 miles by running,
[tex]\rm t = \dfrac{6\ miles}{s}[/tex]
Since the speed of Marina's bicycle is 9 miles per hour faster than she runs. Time is taken by Marina to cover a distance of 19. 5 miles by bicycle,
[tex]\rm t = \dfrac{19.5\ miles}{s+9}[/tex]
We know that Marina can bicycle 19. 5 miles at the same time it takes her to run 6 miles. therefore,
[tex]\rm t = \dfrac{6\ miles}{s}= \dfrac{19.5\ miles}{s+9}[/tex]
[tex]\dfrac{6}{s}= \dfrac{19.5}{s+9}[/tex]
Solving the given equation we will get,
[tex]\rm s = 4\ miles/hr[/tex]
Hence, the speed by which Marina runs is 4 miles/ hr.
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