Question 166792
They both will have gone the same distance 
when they meet.
Let {{{d}}}= the distance they both travel
Let {{{t}}}= the time elapsed during the 1st car's trip
For 1st car:
{{{d = r*t}}}
{{{d = 72t}}}
For the 2nd car
{{{d = 90*(t - 1)}}}
Since both {{{d}}}'s are equal,
{{{72t = 90*(t - 1)}}}
{{{72t = 90t - 90}}}
{{{18t = 90}}}
{{{t = 5}}}hrs
The 2nd car's elapsed time is
{{{t - 1}}}
{{{5 - 1 = 4}}}hrs
The 2nd car overtakes the 1st car in 4 hours
Check the answer:
For the 1st car
{{{d = 72*5}}}
{{{d = 360}}}km
For the 2nd car
{{{d = 90*4}}}
{{{d= 360}}}km
OK