Question 607301
Two  trains  150m  and  160m  long  are  going  in  the  same  direction   at  42 km  and  73 km  per  hour  respectively.How  long  will  it  take    to  pass  each  other? 
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The faster train has to travel from the point when its front is adjactent to the slower train's rear until the faster train's reas is adjactent to the slow train's front.
That's 150 + 160 meters = 310 meters = 0.31 km
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The difference in speed is 73 - 42 = 31 km/hr
t = d/r = 0.31/31 = 0.01 hours
= 36 seconds