1,051,200. A traffic light installed a year ago it has changed 1,051,200 times since it was installed.
To solve this problem, we have to know that one hour has 3,600 seconds. Then, one day has 24 hours which means a day it has 86,400 seconds. If we divide the 86,400 seconds by 30 seconds (the rate of change of the traffic light), we obtain that in a day the traffic light changed 2880 times.
A year has 365 days, if we multiply the amount of change in one day by 365 days of an entire year, we obtain that the traffic light has changed 1,051,200 times after a year that it has been installed.
