- 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?
(1) 30 (2) 24 (3) 20 (4) 60
Solution:
Red light flashes every 20 seconds
Green light flashes every 24 seconds
Therefore, they will flash together every 120 seconds
In every hour they will flash 3600/120 = 30 times
