Question 1034960
200 out
200 back
9 hrs total
d= st
d/s = t
{{{200/x+200/(x-10) = 9}}}
{{{400(x-5)/x(x-10) = 9}}}
{{{400(x-5) = 9x(x-10)}}}
{{{400x-2000 = 9x(x-10)}}}
{{{400x-2000 = 9x^2-90}}}
{{{9x^2+490x-2000 = 0
{{{-((x-50)(9x-40))= 0}}}
Multiply times -1
{{{(x-50)(9x-40)= 0}}}
{{{x-50 = 0}}} or {{{9x-40 = 0}}}
{{{x = 50}}} or {{{9x = 40}}}; {{{x = 40/9}}}
So, on the way out her speed was 50mph and on the return 50-10=40
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Check:
50+40 = 90; 90/2 = 45; 45*9 = 405 it should be 400, the 5 is the result of rounding numbers. So the answer is correct.