Question 1197435


Let {{{n}}} be the {{{slower}}} speed. Then:

{{{100/n+120/(n+10)=4}}}

{{{100n+1000+120n=4n^2+40n}}}

{{{4n^2-180n-1000=0}}}

{{{n^2-45n-250=0}}}

{{{(n+5)(n-50)=0}}}

{{{n=50 (km/h)}}}  for the slower speed, 
and
{{{(n+10)=60( km/h)}}} for the faster speed