Question 1102184
<pre>
                 SPEED      TIME          DISTANCE

WWIND            r+30       60/(r+30)     60

AGNSTWIND        r-30       60/(r-30)     60

TOTAL                         1.3
</pre>

{{{60/(r+30)+60/(r-30)=13/10}}}

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multiply both sides by {{{10(r+30)(r-30)}}};

{{{600(r-30)+600(r+30)=13(r^2-900)}}}

{{{600r-18000+600r+1800=13r^2-13*900}}}

{{{1200r=13r^2-11700}}}

{{{highlight_green(13r^2-1200r-11700=0)}}}

(discriminant, {{{569*60^2}}} )

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{{{highlight_green(r=(1200+60*sqrt(569))/26)}}}


{{{highlight(r=101.2)}}}