A starts at 11:00AM and travels at a speed of 4km/hr. B starts at 1:00PM and travels at 1km/hr for the first 1hr and 2km/hr for the next hr and so on. At what time they will meet each other ?

• though there is no mention of direction,we hav to consider that both A&B starts from same side.
  let at the end of 10hr(i.e at 9pm from 11am),A travelled 40kms in 10hr and B travelled 36kms(1+2+..+8)in 8 hr.
  we cant take 11 hr bcoz after 11hr(i.e at 10pm)B has crossed A.
  so,A & B are (40-36)=4kms far from each other.
  now speed of A=4km/hr & B=9km/hr.
  relative speed= 9-4=5km/hr.
  so,time taken by them to meet= (4/5)hrs=48min.
  so A and B meet At 9:48pm.(Ans)
  
• 13 years agoHelpfull: Yes(24) No(0)
• At 9.48 PM.
  
  At 9 pm, A has travelled 40 kms in 10 hrs and B has travelled 36 kms ( 1+2+3+...+8) in 8 hrs.
  Now speed of A is 4 km/hr and speed of B is 9 km/hr.
  Relative speed = 5 km/hr.
  
  Distance between A and B = 40-36=4 kms.
  
  Time taken by B to cover this additional distance = 4/5 hrs or 48 mins.
  
  so B will meet A at 9.48 PM.
• 13 years agoHelpfull: Yes(15) No(0)
• Train A keeps going at 4 kmph - So every hour, it covers 4 kms.
  
  Train B keeps increasing its speed, so it covers 1 km, 2kms, 3kms so on in consecutive hours.
  
  So, after 'x' hours, distance B traveled = 1+2+3+..+x = x*(x+1)/2
  
  For the trains to meet, this must be equal to how much A traveled = initial distance + x*4kmph
  = 8 + 4x
  
  x*(x+1)/2 = 8+4x
  => x^2 + x = 16 + 8x
  => x^2 - 7x -16 = 0
  a=1, b=-7, c=-16
  
  => x =(approximately) 8.815 or -1.815 (not possible)
  
  So, they will meet after 8.815 hours = 8 hours, 48 minutes 54 seconds (approximately) after B started
  ie, they will meet at 9:48:54 PM
  
• 10 years agoHelpfull: Yes(4) No(0)
• 10:22pm.
  time a b
  11 4 0
  12 8 0
  1 12 0
  2 16 1
  3 20 3
  4 24 6
  5 28 10
  6 32 15
  7 36 21
  8 40 28
  9 44 36
  10 48 45
  11 52 55
• 10 years agoHelpfull: Yes(3) No(4)
• hrs a b
  11 0 0
  12 4 0
  1 8 0
  2 12 1
  3 16 3
  4 20 6
  5 24 10
  6 28 15
  7 32 21
  8 36 28
  9 40 36
  10 44 45
  so answer is just less than 10..check d options
• 10 years agoHelpfull: Yes(1) No(0)
• in which direction they start? either opposite side or same side. if they start travels same side then from which place they start? either same place or certain distance between them????????
• 13 years agoHelpfull: Yes(0) No(8)
• https://www.youtube.com/watch?v=KwFtoisj0Kg
• 6 years agoHelpfull: Yes(0) No(0)