Q. A red light flashes 3 times per minute,green light flashes in 4 minute and yellow light flashes in 6 minute at regular intervals.If all three lights start flashing at the same time how many time do they flash together in each 75min?

• LCM (3,4,6)=12
  quotient of 75 by 12=6
  At the time of starting also they flash together.
  So answer is (6+1)=7
• 9 years agoHelpfull: Yes(11) No(4)
• seconds in a minute = 60.
  no of times red flashes every minute = 3 times.
  no of times green flashes every minute = 4 times
  no of times red flashes every minute = 6 times.
  
  So, red flashes every 60/3 = 20 seconds.
  green flashes every 60/4 = 15 seconds
  yellow flashes every 60/6 = 10 seconds.
  
  Now LCM (10,15,20) = 60 seconds
  so they blink together at every minute.
  
  In 75 minutes, they flash 75 times.
• 8 years agoHelpfull: Yes(6) No(0)
• 6+1 = 7 time
• 9 years agoHelpfull: Yes(2) No(3)
• ans = 6 time
• 9 years agoHelpfull: Yes(1) No(6)
• LCM (3,4,6)=12
  ans= quotient of 75 by 12=6
  :)
• 9 years agoHelpfull: Yes(0) No(4)
• LCM of 3, 4, 6 i s12
  75 / 12 = 6 times
  initially the lights are flashes
  so answer is 6 + 1 = 7
• 9 years agoHelpfull: Yes(0) No(1)
• Ans:-7
  they flash together at every 12th minute and when started
  so 1+6=7times
• 9 years agoHelpfull: Yes(0) No(0)
• LCM of 3,4,6 is 12.
  quotient we get by dividing 75/12 is 6.
  when they start to flash together,for that we consider 1 time. so all together they flash 6+1=7times
• 9 years agoHelpfull: Yes(0) No(1)
• 7 times
  lcm (3,4,6)=12
  so 75/12=6(consider only quotient)
  and they flash at time 0 together(at the start)
  so 6+1=7
• 9 years agoHelpfull: Yes(0) No(1)
• what if the question is given as a red light flashes in 3 min....rest are same.... will the solution varies...please reply soon
• 9 years agoHelpfull: Yes(0) No(2)
• 255 because red light=75*3=225,green=75/4=18,yellow=75/6=12,total=225+18+12=255
• 8 years agoHelpfull: Yes(0) No(0)
• Don't waste your time by doing the problem....no need to answer this type of questions just we have to check either we will get the answer with given data or not
• 8 years agoHelpfull: Yes(0) No(0)