SOLUTION: A train,120m long,travelling at 78km/hr overtakes another train in the same direction at 60km/hr and passes it completely 70seconds.find the length of the 2nd train.

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Question 645393: A train,120m long,travelling at 78km/hr overtakes another train in the same direction at 60km/hr and passes it completely 70seconds.find the length of the 2nd train.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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A train, 120m long,traveling at 78km/hr overtakes another train in the same
direction at 60km/hr and passes it completely 70 seconds.
find the length of the 2nd train\
:
let x = the length of the 2nd train.
Change the speeds into meter/sec
%2878%2A1000%29%2F3600 = 21.67 m/sec
%2860%2A1000%29%2F3600 = 16.67 m/sec
:
Write a time equation, time = dist/speed
:
Length of the two trains divided by the relative speed = 70 seconds
%28120%2Bx%29%2F%2821.67-16.67%29 = 70
:
%28120%2Bx%29%2F5 = 70
120 + x = 5(70)
x = 350 - 120
x = 230 meters the length of the 2nd train