the average speed of the express train is 20 km/hr more than the average speed of a passenger train to cover a distance of 360 kilometres .Express train takes 3 hours less than that of the passenger train find the average speed of passenger train and Express train.
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let speed of passenger train = X km/h
then speed of express train =X+20 km/h
we know,
time =distance/speed
a/c to question,
360/X -360/(X +20) = 3
360 {1/X - 1/(X + 20) } = 3
120(X +20-X)/(X²+20X) =1
2400 = X² + 20x
X² + 20X -2400 = 0
X = { -20± √(400+9600)}/2
=(-20±100)/2 = -60 , 40
X = 40 km/h
hence
speed of passenger train =40 km/h
speed of express train= 60 km/h
then speed of express train =X+20 km/h
we know,
time =distance/speed
a/c to question,
360/X -360/(X +20) = 3
360 {1/X - 1/(X + 20) } = 3
120(X +20-X)/(X²+20X) =1
2400 = X² + 20x
X² + 20X -2400 = 0
X = { -20± √(400+9600)}/2
=(-20±100)/2 = -60 , 40
X = 40 km/h
hence
speed of passenger train =40 km/h
speed of express train= 60 km/h
prajwal4:
pls say me what is meant by 360/X-360/X+20
pls ans me quickly
360/X is time 360 k m is distance and X km/h is speed , km/km/h = h time =distance/speed
also ask questions , express take 3 hour less time then passenger
so, time taken by passenger-time taken by express = 3
so, 360/x -360/(x +20) = 3
thanks a lot,,,,
but pls try to ans my other question pls do it
pls,pls
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