math
posted by bob .
a freight train that is 1 mile long is traveling at 60mph. a second train that is 2 miles long is traveling 40mph. the trains are moving in opposite directions on parallel tracks. how many seconds does it take between the time their locomotives meet and their cabooses fully pass each other?

relative velocity=100mi/hr
distance: 2 miles
timeinhrs= distance/velocity convert that to seconds. 
wouldnt the distance be 3 miles though if the one mile train must travel 1 mile (distance of itsself) plus the distance of the other train which is 2 miles?

1.8 minutes