Question 1145620
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The distance d(x) from the starting line x seconds after the race started (provided x >= 5) is


    d(x) = 45 + {{{((85-45)/(10-5))*(x-5)}}} = 45 + 8*(x-5).


It is the standard interpolation/extrapolation linear function, based on given data.


Linear interpolation/extrapolation formula is applicable in this case,
since after 5 seconds Nick runs with uniform speed.


His speed is  {{{(85-45)/(10-5)}}} = {{{40/5}}} = 8 meters per second.
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