Question

At an intersection, the red light of route A is red for 60 seconds and the other two lights are red for 45 and 75 seconds, respectively. What is the probability that a car traveling from route A will encounter a red light at an intersection?

Answer 1

1/3

Explanation:

The probability of an event E in a sample space S is P(E) = desired outcome/total number of possible outcomes.

The probability of encountering a red light at the intersection P(red light on) = time it takes red light to stay on/total time all the lights stay on, where desired outcome = time it takes red light to stay on on route A and total number of possible outcomes = total time all the lights stay on.

Since all the other two lights have to come on after the red light goes off and before the red light comes on again, and the red light has to be on to encounter it at an intersection.

So, P(red light on) = 60 s/(60 s+ 45 s+ 75 s)

= 60 s/180 s

= 1/3