Question 1130964
<pre>
                SPEED        TIME         DISTANCE

GOING            r+11        510/(r+11)     510

RETURNING        r           510/r          510

TOTAL                        17
</pre>
{{{510/(r+11)+510/r=17}}}

.

.
{{{r^2-49r-330=0}}}

{{{discriminant}}}, {{{61^2}}};

{{{r=(49+61)/2}}}

{{{highlight(r=55)}}}------the speed returning