<PRE><B>Question 233593</B>
Distance(d) equals Rate(r) times Time(t) or d=rt;  r=d/t and t=d/r
Let d=total distance covered

Time spent by rail=(d/2)/75
Time spent by car=(d/2)/45

Now we are told that the above two times add up to 12 hr, so:
(d/2)/75  + (d/2)/45=12 simplify
d/150 +d/90 = 12 or  multiply each term by 450 (LCM)
3d+5d=5400
8d=5400
d=675 mi-------------------total distance covered

CK
Time spent by rail=(675/150)=4.5 hr
Time spent by car=(675)/90=7.5 hr
7.5 +4.5=12
12=12


Hope this helps---ptaylor

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