Question 484322
Probability = (number of events that meet the requirements) / (total number of events)


Here, the probability will be (number of seconds that meet the requirements)/(number of total seconds).  The numerator is the number of seconds that meet the requirement of NOT GREEN.  That happens when the light is red or yellow: 25 + 5 = 30 seconds.  The total number of seconds in a given rotation between green, yellow, and red is 25 + 5 + 55 = 85 seconds.  That is our total number of seconds, and will be the denominator.


So, our probability is {{{30/85}}}, which reduces to {{{6/17}}} or about 0.35.