) In a circular racetrack of length 100 m, three persons A, B and C start together. A and B start in the same direction at speeds of 10 m/s and 8 m/s respectively. While C runs in the opposite direction at 15 m/s. When will all the three meet for the first time on the track after the start?
a) After 4 s
b) After 50 s
c) After 100 s
d) After 200 s
e) None of these

• A takes (100m) / (10m/s) = 10s to finish one complete round.
  B takes (100m) / (8m/s) = 12.5s to finish one complete round.
  C takes (100m) / (15m/s) = (20/3)s to finish one complete round.
  For them to meet, the time will be LCM of above three times i.e,
  LCM(10,12.5,20/3) = LCM(10,25,20)/GCD(1,2,3)=100/1=100sec
• 10 years agoHelpfull: Yes(44) No(7)
• After 100 sec
  the option is c
  am i ri8 or am i ri8??
• 10 years agoHelpfull: Yes(6) No(19)
• a) after 4 sec
  in 4 sec a and b goes 40 m and 32 m
  while in 4 sec c goes 60 sec in opposite direction
  so total(40+60)m is coverd in 4 sec by a and c together
• 10 years agoHelpfull: Yes(2) No(4)
• working backword from the option
  option a :
  
  A=>4*10)=40m
  B=>(4*8)=32m
  C=>(4*15)=60m...........so here distance travelled by each person is not a Multiple of 100
  
  So option c is correct
  Answer is C)After 100s
• 10 years agoHelpfull: Yes(1) No(2)
• Since the track is a circular track A and B will meet every 50 seconds. i.e. 100 / (10-8).
  Since it is a multiple of 50 they will be meeting at the starting point every 50 Seconds.
  If you multiply 15 x 50 you will get 750 and after the second 50 it will be 1500.
  All of them will meet at the starting point after 100s
• 9 years agoHelpfull: Yes(1) No(0)
• after 100sec
• 10 years agoHelpfull: Yes(0) No(1)
• How ? will You explain the answer ?
  
• 10 years agoHelpfull: Yes(0) No(0)
• Ans: After 100s
• 10 years agoHelpfull: Yes(0) No(0)
• both c and d are corrrect
• 10 years agoHelpfull: Yes(0) No(1)
• Ans : 200s , 100Sec is starting time. 200 sec is correct first time after the start
• 10 years agoHelpfull: Yes(0) No(0)
• According to formula :
  time taken to meet for the first time= LCM of{100/(15-8) , 100/(15-10)}
  = LCM of{100/7 , 100/5}
  {LCM of 100 is =100 and HCF of 7 and 5 is=1}
  so, =100/1
  =100 sec
  100 sec is the final ans
  
• 9 years agoHelpfull: Yes(0) No(0)
• after 100s
• 8 years agoHelpfull: Yes(0) No(0)
• Diff speed a and b is 2
  Opsitr speed a and c is 25
  Opsite speed b and c is 23
  A and b meet 400 m meet
  In this case c oppsite so
  25×23=575
  575m meets a,b and c 575×4 =2300m
  575÷8
  71.875 least so above 50 s
• 6 years agoHelpfull: Yes(0) No(0)