3 wheels make 60,36 and 24 revolutions per min respectively. There is a red spot on the rim of all the 3 wheels. If the red spot was at the bottom most point when they started after how much time would they be at the bottom most point again?

• They will be together after the L.C.M of the times taken by them to make one revolution
  
  Hence the time taken by 1st wheel to make one revolution = (1/60) min
  
  Second wheel to make one revolution = (1/36) min
  
  Third wheel to make one revolution = (1/24) min
  
  Hence L.C.M of the times taken by them to make one revolution = L.C.M.of(1/60,1/36,1/24) min.
  
  = (1/12) min
  
  i.e. after 5 sec.
  
  This is correct.
  
• 12 years agoHelpfull: Yes(11) No(1)
• Mr PP Singh not 12 sec it is 5 sec
  
  after 5 sec
  
  1 st one will make 5
  2 nd one will make 3
  3 rd one will make 2
  
  so the ans is 5 sec,
  
  sorry,
  
  not a LCM of 60,36,24 it is LCM of 1/60,1/36,1/24
• 12 years agoHelpfull: Yes(4) No(0)
• 5.167 sec.........lcm of 1/60,1/36,1/24
• 11 years agoHelpfull: Yes(3) No(1)
• After 12 secs or 1/12 mins.
  
  In 1/12 mins, first wheel will make 5 revolutions.
  In 1/12 mins, 2nd wheel will make 3 revolutions.
  In 1/12 mins, 3rd wheel will make 2 revolutions.
• 12 years agoHelpfull: Yes(2) No(3)
• I think PP Singh is right.
  
  Why to take LCM of 60,36,24 ?
  
  We should take LCM of 1/60 , 1/36, and 1/24 mins.
  LCM of 1/60 , 1/36, and 1/24 mins. = 1/12 mins
  
  After 5 secs or 1/12 mins, all 3 will be have red spot at bottom most point.
• 12 years agoHelpfull: Yes(2) No(0)
• Ans. After 360 minutes i.e 6 hours
  
  Take LCM of 60,36 and 24 which will be 360
• 12 years agoHelpfull: Yes(1) No(5)
• do the LCM of 60,36,24 so the answer is 360 min.
• 12 years agoHelpfull: Yes(0) No(5)
• L.C.M of 60,36,24 is 360
  so after 6 hours the red spot in all the three wheel reaches the bottom
• 12 years agoHelpfull: Yes(0) No(4)
• LCM of (1/60,1/36,1/24) after 5 sec they be at the bottom most point
• 12 years agoHelpfull: Yes(0) No(0)
• ans=360,for common point take LCM of three revolution times
• 12 years agoHelpfull: Yes(0) No(2)