<PRE><B>Question 229669</B>
An express train travels 90 km per hour from A to B.
 A local train takes 2.5 hours longer to travel the same distance at 50 km per hour. 
How far apart are A and B? 
:
Let d = dist from A to B
;
Write a time equation: Time = {{{dist/speed}}}
:
Slow train time = Fast train time + 2.5 hrs
{{{d/50}}} = {{{d/90}}} + 2.5
:
Multiply equation by 450 to get rid of the denominators, results
9d = 5d + 2.5(450)
9d - 5d = 1125
4d = 1125
d = {{{1125/4}}}
d = 281.25</PRE>