A red light flashes 3 times per minute and a green light flashes 5
times in two minutes at regular intervals. If both lights start flashing at the
same time, how many times do they flash together in each hour?
(a) 30 (b) 24
(c) 20 (d) 60

• a) 30
  Rate of flashing for Red light=3 times per minutes=Once in 20 sec.
  Similarly for Green Light=5 times per 2 minutes=Once in 24 sec.
  The time they flash together=120 sec. or 2 minutes.
  Therefore in 1 Hour,they flash together 60/2 =30 times
• 12 years agoHelpfull: Yes(10) No(1)
• Rate of flashing for Red light=3 times per minutes=Once in 20 sec
  Similarly for Green Light=5 times per 2 minutes=Once in 24 sec.
  Red: 20,40,60,80,100,120 sec in 2 min
  Green:24,48,72,96,120 sec in 2 min
  so together 2 times in 2 min
  so 6o times in 1 hr(ans)
• 12 years agoHelpfull: Yes(1) No(7)
• answer is 30 times
  
  20,40,60,80,100,120 sec in two mins
  24,48,72,96,120 sec two mins
  so red and green lights flashes 1 time for every 2 mins,we have 60 mins for 1hour
  2mins=1time
  60mins=30 times
  
  so ans is 30 times
• 11 years agoHelpfull: Yes(0) No(0)