two friends suppose A and B run on circular track in clockwise and anti- clockwise direction respectively . A runs 1 km in 4 minutes. What should be the speed of B so that they meet 24 times in 45 minutes.
1. 17 2. 18
other options I not remember.

• You missed 1 thing. Length of the track was given. It was 1 KM. And the ques was that A runs 1 round in 4 minutes. Answer would be 17 KM/hr.
  
  A runs 1 KM in 4 min. So, A's speed = 15 KM/hr.
  
  Suppose, they meet in x hr. It means they will complete 1 round i.e. 1 km in x hr.
  
  Let B's speed = y KM/hr.
  
  then, 15x + yx = 1.
  => x(15+y) = 1
  => x = 1/(15+y)
  
  So, to complete 1 round they take 1/(15+y) hr.
  
  Now, according to ques they complete 24 round in 45 min. i.e. 3/4 hr.
  
  So, 1(15+y)*24 = 3/4 .
  
  Putting y = 17 KM/hr we will get our answer.
• 9 years agoHelpfull: Yes(7) No(0)
• one more approach:
  
  by the concept of relative velocity..
  
  A runs 1 KM in 4 min. So, A's speed = 15 KM/hr.
  
  let speed of B=x
  
  as B is moving in opposite direction, so by the concept of relativity we can assume,
  
  speed of B=15+x
  24th round takes 45 min(3/4 hr)
  1 round will take 3/(24*4) hrs
  
  therefore relative distance travelled by B=1km
  relative speed of B * time taken to complete 1 round =1 km
  
  i.e, (15+x)*3/(4*24)=1
  15+x=32
  
  hence x=17 km/hr
• 9 years agoHelpfull: Yes(5) No(0)
• Data Inadequate....because we don't know about length of track..
• 9 years agoHelpfull: Yes(2) No(0)
• Ans 18km/hr
• 9 years agoHelpfull: Yes(1) No(1)
• Data Inadequate
• 9 years agoHelpfull: Yes(0) No(0)
• please explain how 18km/hr
• 9 years agoHelpfull: Yes(0) No(0)
• ans -17 check
• 9 years agoHelpfull: Yes(0) No(0)