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time speed dist

by mitaliisrani » Thu Sep 02, 2010 9:55 pm
Two trains T1 T2, which are 539 km apart start at the same time, move towards each other. They just complete crossing each other in 3hrs 20 mins. fIND THE DIFFERENCE BETWEEN THE LENGTHS OF THE TWO TRAINS, GIVEN THAT THEIR LENGTHS ARE IN THE RATIO 2:3 AND THEIR SPEEDS ARE 25M/S and 20m/s respectively
A) 100m
B) 200m
C) 500m
D) 150m

OA is
B
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by Rahul@gurome » Thu Sep 02, 2010 11:03 pm
Solution:
Let the length of the trains be 2x and 3x.

So the distance being covered in 3hrs 20 minutes is 539 + 2x +3x = 539+5x.

Their speeds are 25m/s and 20m/s.
Or relative speed is (25+20) = 45m/s = 162km/hr since the two trains are moving in opposite directions.

So (539+5x)/162 = 3 + 20/60 hrs = 10/3
Or 539 + 5x = 540.
Or x = 1/5 km = 200m.

The correct answer is (B).
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