Question 36033
Let x be the speed
Equation:
{{{200/x-200/(x+10)=1}}}
200[(x+10)-(x)]=(x)(x+10)
{{{200(10)=x^2+10x}}}
{{{2000=x^2+10x}}}
{{{x^2+10x-2000=0}}}
Factor:
x=-50 or x=40
Hence, his speed was 40mph.
Paul.