A fast train takes 3 hours less than a slow train for a journey of 900 km, If the speed of the slow train is 15 km/hr less than that of the fast train, the speeds of the slow train is (1) 50 km/hr (2) 75 km/hr (3) 60 km/hr (4) 45 km/hr

• Let the speeds are =x,x-15
  900/x-15 - 900/x= 3
  300x-300x+4500=x^2-15x
  x^2-15x -4500=0
  (x-75)(x+60)=0=>x=75kmph
  Slower train speed=75-15=60kmph
• 4 years agoHelpfull: Yes(5) No(1)
• Let speed taken by slow train be x
  thus, speed taken by fast train be (x+15)
  time by slow train=900/x
  time by fast train=900/x+15
  time taken by slow train-time taken by fast train=3
  900/x-900/x+15=3
  by cross multiplication we get,
  900x
  13500-900x/x(x+150)=3
  by solving these equation we get,
  (x-50)(x-45)=0
  x=50 x=45
  speed of slow train is x-15= 50-15=45
  thus the ans is option 4=45km/hr
• 4 years agoHelpfull: Yes(1) No(2)
• Let the time taken by the slow train be x hr
  A/c to question,
  the time taken by the fast train is 3 hr less than slow train
  i.e time taken by the fast train is (x-3) hr
  
  Let the speed of the fast train be y km/hr
  then,
  A/c to question,
  the speed of the slow train is (y-15) km/hr
  we are given with the distance covered is 900 km
  we know that,
  
  [DISTANCE=SPEED *TIME]
  
  from above formula;
  (y-15)*x = (x-3)y
  yx-15x = xy-3y
  i.e
  y=5x
  
  putting the value of y=5x in speed of slow thain ,we get
  x(5x-15)=900 [distance=speed*time]
  ...........
  ...........
  solving the equation ,we get
  x(x-15) + 12(x-15)=0
  x = -12 (not possible)
  x = 15 (possible)
  
  putting the value of x in above equation ,we get
  y = 15 * 5
  i.e y = 75
  now,
  putting the value of y in the speed of slow train, we get
  
  speed of slow train = (y - 15) km/hr
  =(75 - 15) = 60 km/hr
  i.e
  speed of slow train is 60 km/hr
• 4 years agoHelpfull: Yes(1) No(1)
• simply trail for the each option and check the time taken for slow train and fast train differnce should be 3 hours.(Answers is 60km/hr)
• 3 years agoHelpfull: Yes(0) No(0)
• 3. 60 km/hr
• 3 years agoHelpfull: Yes(0) No(0)
• As per Questions
  distance for both=900km
  let speed of fast train=x.speed of slow train=x-15
  let time for slow train =t.time for fast train=t-3
  As distance is same for both so equating we get
  x(t-3)=(x-15)t
  here we get ratio of x/t=5
  
  as distance is 900km
  so substitute in any eequation we get t=15
  so x becomes 75 which is speed of fast train.
  therefore speed of slow train is 75-15=60
• 2 years agoHelpfull: Yes(0) No(0)