Question 1069156
<pre>
                    SPEED      TIME          DISTANCE
HOME to BEACH        r         80/r            80
BEACH to HOME       r*(4/5)    80/(r(4/5))     80
Total                           9
</pre>


{{{80/r+80/((4/5)r)=9}}}


{{{80/r+80*5/(4r)=9}}}


{{{80/r+20*5/r=9}}}


{{{180/r=9}}}


{{{r=180/9}}}


{{{highlight(r=20)}}}, speed from Home to Beach House.


Beach House to Home is 20% slower, {{{20*(0.8)=highlight(16)}}}.