A complete cycle of a traffic light takes 60 seconds. During each cycle the light is green for 25 second, yellow for 5 second and red for 30 second. At a randomly chosen time, the probability that the light will not be green is

To find the probability that the light will not be green, we first determine the total duration of the cycle and the duration when the light is not green.

The total duration of one cycle is 60 seconds.

The duration when the light is green is 25 seconds. Therefore, the duration when the light is not green is the sum of the yellow and red light durations, which is 5 seconds plus 30 seconds, equaling 35 seconds. Alternatively, you can subtract the green time from the total time: 60 minus 25 equals 35 seconds.

The probability is calculated by dividing the duration when the light is not green by the total cycle duration. This gives 35 divided by 60.

By simplifying the fraction 35/60 by dividing both the numerator and the denominator by 5, we get 7/12.

Thus, the probability that the light will not be green is 7/12. The correct option is D.