Q. A train 120 meters long passes an electric pole in 12 seconds and another train of same length traveling in opposite direction in 8 seconds. The speed of the second train is

Option
A 60 Km
B 66 Km
C 72 Km

• Option: C
  speed of first train=120/12=10 m/s
  let speed of second train be x m/s. As they are approaching each other, relative speed is (10+x) m/s.
  distance between each other is 120+120=240 m.
  time of crossing each other is 8 sec
  =>240/(10+x)=8
  =>x=20m/s = 20*18/5 km/hr = 72 kmph
• 13 years agoHelpfull: Yes(31) No(1)
• 120/8=15m/s
  15m/s=54km
  there is no option pls check the options
• 13 years agoHelpfull: Yes(7) No(14)
• length of 1st train(L1)=120m
  length of 2n train(L2)=120m
  time taken by 1st train(t1)=12sec
  time taken by 2nd train(t2)=8sec
  speed of 1st train(s1)= L1/t1=120/12=10m/sec
  so t2=(L1+L2)/(s1+s2)
  => 8= 240/(10+s2)
  => s2= 20m/sec
  so 20m/sec * 18/5= 72 km/hr( ans)
  so
• 12 years agoHelpfull: Yes(7) No(1)
• Solution.
  The train which is 120 metres in length crosses a pole in 12 seconds implies it is covering the distance 120 metres in 12 seconds.
  So speed of this train is 120/12 = 10 m/s.
  It is crossing another train traveling in opposite direction in 8 seconds.
  Let the speed of this train be y.
  It’s length is also 120 metres.
  So (120+120)/(10+y) = 8.
  Or 10+y = 30.
  Or y = 20 m/s or 20*18/5 km/hr = 72 km/hr
  
  The correct answer is C.
• 12 years agoHelpfull: Yes(5) No(1)
• speed of first train=120/12=10 m/s
  let speed of second train be x m/s. As they are approaching each other, relative speed is (10+x) m/s.
  distance between each other is 120+120=240 m.
  time of crossing each other is 8 sec
  =>240/(10+x)=8
  =>x=20m/s = 20*18/5 km/hr = 72 kmph
• 13 years agoHelpfull: Yes(3) No(0)
• Speed of Train 1=120/12=10 m/s
  let speed of train2 is x m/s. so relative speed is (10+x) m/s.(because running in opp dir)
  length of both the train is 120+120=240 m.
  time of crossing each other is 8 sec
  i.e 240/(10+x)=8 hence 30=20+x;
  i.e.x=20m/s so speed is 20*18/5 km/hr = 72 kmph
• 12 years agoHelpfull: Yes(3) No(0)
• Ans: C 72 Kmph
  Train covers 120 meters in 12 seconds, therefore
  speed of first train = 120/12=10 m/s
  let speed of second train be x m/s. Trains are approaching each other, thereore there relative speed is (10+x) m/s.
  Trains have to covere distance equal to the sum of length of both trains which is 120 + 120 = 240 m.
  time taken to cross the trains i.e. 240 m is 8 sec
  Thus 240/(10+x) = 8 , by solving we get
  x = 20 m/s = 20*3600/1000 km/hr = 72 kmph
• 13 years agoHelpfull: Yes(2) No(0)