Question 1124965
<pre>
               SPEED      TIME      DISTANCE
FirstPart      r          325/r      325
SecondPart    r-30       35/(r-30)   35
Total                       6
</pre>


{{{325/r+35/(r-30)=6}}}

-


{{{325(r-30)+35r=6r(r-30)}}}
{{{360r-9750=6r^2-180r}}}
{{{6r^2-180r-360r+9750=0}}}
{{{r^2-30r-60r+1625=0}}}
{{{r^2-90r+1625=0}}}


{{{r=(90+sqrt(8100-4*1625))/2}}}

{{{r=45+sqrt(81*25-1625)}}}

{{{r=45+sqrt(400)}}}

{{{r=45+20}}}

{{{r=65}}}