Answers

  • Brainly User
2014-10-06T21:01:00+05:30
Original time taken by the passenger train = x
distance = 140 km
time taken by the passenger train = x-3
normal speed = a
travelled speed = a +42
speed = d/t
d = speed *t
(x-3)(a + 42) = xa
xa +42x -3a -126 =xa
42x = 3a +126 =140
3a = 140 - 126
3a = 14
a = 14/3 Kmph

0
2014-10-06T21:06:53+05:30

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Let the normal speed of train = x km/h
time taken to cover 140 km =  \frac{140}{x}  h

 If the speed is increased by 42 km/h from its normal speed, journey becomes 3 hours less.
   speed = (x+42)km/h
  time  =  \frac{140}{x+42}

 \frac{140}{x}- \frac{140}{x+42}= 3

140( \frac{1}{x}- \frac{1}{x+42})=3

140( \frac{(x+42)-x}{x(x+42)} )=3

140*42 = 3x(x+42)

3 x^{2} +126x-5880=0

Solving the equation, we get x= 28 or -72. ignore -72 as speed can't be negative.

So the normal speed of train is 28 km/h


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