Question 1201248
<pre>
Using the description

            SPEED        TIME          DIST.

USUAL       r            18/r            18

FASTER      r+1/2       18/(r+1/2)       18 

DIFFERENCE                1/2
</pre>
{{{18/r-18/(r+1/2)=1/2}}}---------simplify and solve.


{{{36/r-36/(r+1/2)=1}}}

{{{36(r+1/2)-36r=r(r+1/2)}}}

{{{36r+18-36r=r(r+1/2)}}}

{{{18=r(r+1/2)}}}

{{{r^2+r/2-18=0}}}

{{{r^2+(1/2)r-18=0}}}

discrim,{{{1/4-4(-18)=72&1/4}}}
{{{r=(-1/2+ sqrt(72&1/4))/2}}}

{{{highlight(r=4)}}}